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The focus of this paper was to investigate the spatial and temporal variability of dry and wet events using the standard precipitation and evapotranspiration index (SPEI) in the Tana River Basin (TRB) in Kenya. The SPEI is a new drought index which incorporates the effect of evapotranspiration on drought analysis thus making it possible to identify changes in water demand in the context of global warming. The SPEI was computed at 6- and 12-month timescales using a 54-year long monthly rainfall data from the Global Precipitation and Climate Center (GPCC) and temperature data from the Climate Research Unit (CRU) both recorded between 1960 and 2013. Both datasets have a spatial resolution of 0.5° by 0.5° and were extracted for every grid point in the basin. The SPEI was used to assess the temporal and spatial evolution of dry and wet events as well as determine their duration, severity, and intensity. The evolution of significant historical dry and wet events and the frequency of occurrence were clearly identified. The index showed that the period between 1960 and 1980 was dominated by dry events while wet events were dominant in the period between 1990 and 2000. The SPEI6 had the longest duration of dry events of 30 months and severity of 44.67 which was observed at grid 5while the highest intensity was 2.18 observed at grid 31. Grid 19 had the longest duration (52 months) and highest severity (88.08) of dry events for SPEI12 and the intensity was highest (1.94) in grid 31. The longest duration (23) and highest severity (40.03) of wet events for SPEI6 were recorded in grid 39. The highest intensity of wet events for SPEI6 was 1.91 at grid 23 and 1.81 at grid 37 for SPEI12. The principal component analysis (PCA) was applied to the SPEI time series in order to assess the spatial pattern of variability of the dry and wet events in the basin. The PCA showed that there were two leading components which explained over 80% of the spatial variation of dry and wet events in the basin. Further, the continuous wavelet transform (CWT) was applied to the PCA scores in order to capture the time-frequency dynamics. The wavelet transform of the SPEI6 and SPEI12 identified significant periodicities of 1 to 2 years across the spectrum. [ABSTRACT FROM AUTHOR]

The statistical characteristics of precipitation play an extremely important role in the risk assessment of drought and flood disasters and water resource management. In this paper, the precipitation concentration degree (PCD), precipitation concentration period (PCP) and precipitation concentration index (PCI) were used to analyse the spatiotemporal variation in precipitation concentration characteristics in China from 1960 to 2015. In addition, the cross-wavelet transform was used to analyse the possible dependencies and spatial characteristics between these three precipitation concentration indices (PCD, PCP and PCI) and monsoon indices (East Asian summer monsoon index, EASMI; South Asian summer monsoon index, SASMI; and South China Sea summer monsoon index, SCSSMI) of nine river basins in China. The results show that the spatial distribution of precipitation concentration indices in China has obvious north-south and east-west variability. China's precipitation concentration indices are generally declining, with weak volatility. Among these indices, the PCD (P < 0.05) and PCI (P < 0.01) have decreased significantly at rates of − 0.005/10 year and − 0.006/10 year, respectively, while there has been no obvious decrease in the PCP. Compared with the PCD before 1978, the PCD in the rainy season after 1978 has decreased. In most areas, the rainy season is concentrated in July every year; however, the rainy season has been delayed in the middle and lower reaches of the Yangtze River and has advanced mainly in the other basins. The PCI has declined since 1978, indicating a decreasing contribution of heavy precipitation to the total annual precipitation, but this change in the PCI has occurred mainly at high-value stations (PCI > 0.7), and the PCI at low-value stations has increased. Most of China's precipitation concentration indices and monsoon indices, as well as the NWRB, have small-scale (2–4 years) or medium-scale (12–15 years) oscillation periods. The oscillation periods between the precipitation concentration indices and monsoon indices in the Yangtze and Pearl River basins are more significant than those in other basins. The results of this study can help to understand the differences among the precipitation concentration characteristics in different basins in China and the intrinsic relationship between these characteristics and the summer monsoon and provide a reference for further research. [ABSTRACT FROM AUTHOR]

This study presents the precipitation changes of the Heihe River Basin (HRB), Northwest China, using a long-term (1980–2014) and highly resolved modeling (up to 3 km by 3 km) with the Regional Integrated Environment Modeling System (RIEMS) forced by ERA-Interim reanalysis data. Firstly, the added value of high-resolution RIEMS simulation nested with ERA-Interim reanalysis was presented by comparisons among the RIEMS simulation results, site-based ground measurements, satellite-retrieved precipitation from TRMM 3B43 (V7), and the EAR-interim reanalysis data. The bias of the ERA-Interim reanalysis was largely corrected by the RIEMS simulation, although a little bias existed in the RIEMS simulation. RIEMS simulation showed that there was an increasing trend in the precipitation of the HRB from 1980 to 2014 with a rate of increase of approximately 3%/year for summer and 5%/year for autumn in the southeast part of the HRB. The increased precipitation mainly resulted from more precipitation days and the strengthening of daily precipitation. Upward motion from strengthened convergence over the eastern part of the HRB was the common reason for increased precipitation in summer and autumn, which was partly offset by decreased water vapor supply in summer while it was strengthened by increased water vapor supply in autumn. This paper presents precipitation changes for the HRB associated with global warming since 1980 and provides a higher-resolution climatological data set useful for reference climate impact studies. [ABSTRACT FROM AUTHOR]

The Yangtze River has been subject to heavy flooding throughout history, and in recent times severe floods such as those in 1998 have resulted in heavy loss of life and livelihoods. Dams along the river help to manage flood waters, and are important sources of electricity for the region. Being able to forecast high-impact events at long lead times therefore has enormous potential benefit. Recent improvements in seasonal forecasting mean that dynamical climate models can start to be used directly for operational services. The teleconnection from El Niño to Yangtze River basin rainfall meant that the strong El Niño in winter 2015/16 provided a valuable opportunity to test the application of a dynamical forecast system. This paper therefore presents a case study of a real-time seasonal forecast for the Yangtze River basin, building on previous work demonstrating the retrospective skill of such a forecast. A simple forecasting methodology is presented, in which the forecast probabilities are derived from the historical relationship between hindcast and observations. Its performance for 2016 is discussed. The heavy rainfall in the May-June-July period was correctly forecast well in advance. August saw anomalously low rainfall, and the forecasts for the June-July-August period correctly showed closer to average levels. The forecasts contributed to the confidence of decision-makers across the Yangtze River basin. Trials of climate services such as this help to promote appropriate use of seasonal forecasts, and highlight areas for future improvements. [ABSTRACT FROM AUTHOR]

Identification of spatial and spatiotemporal precipitation variations plays an important role in different hydrological applications such as missing data estimation. In this paper, the results of Bayesian maximum entropy (BME) and ordinary kriging (OK) are compared for modeling spatial and spatiotemporal variations of annual precipitation with and without incorporating elevation variations. The study area of this research is Namak Lake watershed located in the central part of Iran with an area of approximately 90,000 km. The BME and OK methods have been used to model the spatial and spatiotemporal variations of precipitation in this watershed, and their performances have been evaluated using cross-validation statistics. The results of the case study have shown the superiority of BME over OK in both spatial and spatiotemporal modes. The results have shown that BME estimates are less biased and more accurate than OK. The improvements in the BME estimates are mostly related to incorporating hard and soft data in the estimation process, which resulted in more detailed and reliable results. Estimation error variance for BME results is less than OK estimations in the study area in both spatial and spatiotemporal modes. [ABSTRACT FROM AUTHOR]

Alpine and Mediterranean areas are undergoing a profound change in the typology and distribution of rainfall. In particular, there has been an increase in consecutive non-rainy days, and an escalation of extreme rainy events. The climatic characteristic of extreme precipitations over short-term intervals is an object of study in the watershed of Lake Maggiore, the second largest freshwater basin in Italy (located in the north-west of the country) and an important resource for tourism, fishing and commercial flower growing. The historical extreme rainfall series with high-resolution from 5 to 45 min and above: 1, 2, 3, 6, 12 and 24 h collected at different gauges located at representative sites in the watershed of Lake Maggiore, have been computed to perform regional frequency analysis of annual maxima precipitation based on the L-moments approach, and to produce growth curves for different return-period rainfall events. Because of different rainfall-generating mechanisms in the watershed of Lake Maggiore such as elevation, no single parent distribution could be found for the entire study area. This paper concerns an investigation designed to give a first view of the temporal change and evolution of annual maxima precipitation, focusing particularly on both heavy and extreme events recorded at time intervals ranging from few minutes to 24 h and also to create and develop an extreme storm precipitation database, starting from historical sub-daily precipitation series distributed over the territory. There have been two-part changes in extreme rainfall events occurrence in the last 23 years from 1987 to 2009. Little change is observed in 720 min and 24-h precipitations, but the change seen in 5, 10, 15, 20, 30, 45, 60, 120, 180 and 360 min events is significant. In fact, during the 2000s, growth curves have flattened and annual maxima have decreased. [ABSTRACT FROM AUTHOR]

This paper tried to reconstruct the time series (TS) of monthly average temperature (MAT), monthly accumulated precipitation (MAP), and monthly accumulated runoff (MAR) during 1901-1960 in the Kaidu River Basin using the Delta method and the three-layered feed forward neural network with backpropagation algorithm (TLBP-FFNN) model. Uncertainties in the reconstruction of hydrometeorological parameters were also discussed. Available monthly observed hydrometeorological data covering the period 1961-2000 from the Kaidu River Basin, the monthly observed meteorological data from three stations in Central Asia, monthly grid climatic data from the Climatic Research Unit (CRU), and Coupled Model Intercomparison Project Phase 3 (CMIP3) dataset covering the period 1901-2000 were used for the reconstruction. It was found that the Delta method performed very well for calibrated and verified MAT in the Kaidu River Basin based on the monthly observed meteorological data from Central Asia, the monthly grid climatic data from CRU, and the CMIP3 dataset from 1961 to 2000. Although calibration and verification of MAP did not perform as well as MAT, MAP at Bayinbuluke station, an alpine meteorological station, showed a satisfactory result based on the data from CRU and CMIP3, indicating that the Delta method can be applied to reconstruct MAT in the Kaidu River Basin on the basis of the selected three data sources and MAP in the mountain area based on CRU and CMIP3. MAR at Dashankou station, a hydrological gauge station on the verge of the Tianshan Mountains, from 1961 to 2000 was well calibrated and verified using the TLBP-FFNN model with structure (8,1,1) by taking MAT and MAP of four meteorological stations from observation; CRU and CMIP3 data, respectively, as inputs; and the model was expanded to reconstruct TS during 1901-1960. While the characteristics of annual periodicity were depicted well by the TS of MAT, MAP, and MAR reconstructed over the target stations during the period 1901-1960, different high frequency signals were captured also. The annual average temperature (AAT) show a significant increasing trend during the 20th century, but annual accumulated precipitation (AAP) and annual accumulated runoff (AAR) do not. Although some uncertainties exist in the hydrometeorological reconstruction, this work should provide a viable reference for studying long-term change of climate and water resources as well as risk assessment of flood and drought in the Kaidu River Basin, a region of fast economic development. [ABSTRACT FROM AUTHOR]

Hydrological processes depend directly on climate conditions [e.g., precipitation, potential evapotranspiration ( PE)] based on the water balance. This paper examines streamflow datasets at four hydrological stations and meteorological observations at 79 weather stations to reveal the streamflow changes and underlying drivers in four typical watersheds (Meigang, Saitang, Gaosha, and Xiashan) within Poyang Lake Basin from 1961 to 2000. Most of the less than 90th percentile of daily streamflow in each watershed increases significantly at different rates. As an important indicator of the seasonal changes in the streamflow, CT (the timing of the mass center of the streamflow) in each watershed shows a negligible change. The annual streamflow in each watershed increases at different rates, with a statistically significant trend (at the 5 % level) of 9.87 and 7.72 mm year, respectively, in Meigang and Gaosha watersheds. Given the existence of interactions between precipitation and PE, the original climate elasticity of streamflow can not reflect the relationship of streamflow with precipitation and PE effectively. We modify this method and find the modified climate elasticity to be more accurate and reasonable using the correlation analysis. The analyses from the modified climate elasticity in the four watersheds show that a 10 % increase (decrease) in precipitation will increase (decrease) the annual streamflow by 14.1-16.3 %, while a 10 % increase (decrease) in PE will decrease (increase) the annual streamflow by −10.2 to −2.1 %. In addition, the modified climate elasticity is applied to estimate the contribution of annual precipitation and PE to the increasing annual streamflow in each watershed over the past 40 years. Our result suggests that the percentage attribution of the increasing precipitation is more than 59 % and the decreasing in PE is less than 41 %, indicating that the increasing precipitation is the major driving factor for the annual streamflow increase for each watershed. [ABSTRACT FROM AUTHOR]

The inverse distance method, one of the commonly used methods for analyzing spatial variation of rainfall, is flexible if the order of distances in the method is adjustable. By applying the genetic algorithm (GA), the optimal order of distances can be found to minimize the difference between estimated and measured precipitation data. A case study of the Feitsui reservoir watershed in Taiwan is described in the present paper. The results show that the variability of the order of distances is small when the topography of rainfall stations is uniform. Moreover, when rainfall characteristic is uniform, the horizontal distance between rainfall stations and interpolated locations is the major factor influencing the order of distances. The results also verify that the variable-order inverse distance method is more suitable than the arithmetic average method and the Thiessen Polygons method in describing the spatial variation of rainfall. The efficiency and reliability of hydrologic modeling and hence of general water resource management can be significantly improved by more accurate rainfall data interpolated by the variable-order inverse distance method. [ABSTRACT FROM AUTHOR]

The study data obtained on regional climate changes (surface layer temperature and atmospheric precipitation) in the Ural River basin are reported for a 70-year period (1950–2020). Variations in the basic parameters of the regional climate in the basin studied were obtained by standard statistical data analysis, as well as by calculation of the integral climate anomaly indices. Statistically significant linear trend coefficients illustrate a steady increase in the average annual air temperature in the Ural River basin. The largest contribution to the growth of this parameter is made in the first three months of the calendar year (January–March) and the autumn months (October–November). The long-term course of precipitation values is devoid of unidirectional and statistically significant trends. The important macroregional trend is an increase in precipitation during the cold period. In conclusion, it should be noted that the diverse physical and geographical conditions of the regional climate are indicative of a spatially nonuniform response to the global and macroregional changes. [ABSTRACT FROM AUTHOR]

Precipitation is considered one of the most important forcing data in scientific investigations involving agriculture, water management, and climate variability. Knowledge of precipitation variation during rainy seasons is the key to the understanding of the precipitation variability under the effect of climate change. This study evaluated some rainy season features (e.g., onset, retreat, and rainy-season precipitation) over the Yellow River basin (YRB), China, and the influence of the El Niño-Southern Oscillation (ENSO). The multi-scale moving t-test was applied to capture the onset and retreat of rainy season. The possible linkage between ENSO-induced precipitation and monsoon and atmospheric circulation was also explored. From the analysis, four conclusions can be drawn: (1) Rainy season began the earliest (latest) and ended the latest (earliest) in the southern (northern) YRB, with rainy-season precipitation increasing from northwest to southeast. (2) Rainy-season precipitation showed strong correlation to SST in Niño regions. Precipitation can reach up to 20% above the average precipitation for decaying central Pacific warming (CPW) and down to 35% below the average precipitation for developing eastern Pacific warming (EPW) in most areas of the YRB. (3) Developing El Niño showed the strongest dry signals among developing ENSO and ENSO Modoki phases. Decaying El Niño and El Niño Modoki indicated overall increasing precipitation, with La Niña and La Niña Modoki during the corresponding period showing the opposite tendency. (4) Different performances of ENSO-induced precipitation attributed to the combined influence of the monsoon from the India Ocean and the atmospheric circulation in the Western North Pacific (WNP). Stronger anti-cyclone and monsoon are related to increasing rainy-season precipitation. These findings can improve the predictability of rainy season features and ENSO-induced precipitation. [ABSTRACT FROM AUTHOR]

According to the daily maximum and minimum temperature and the precipitation at 40 meteorological stations in the Daqing River Basin of China during 1980–2015, the spatial and temporal trends of extreme temperature and precipitation are analyzed. The trend strengths, stability, and magnitude are calculated for ten indices of temperature and eight indices of precipitation. The results show that trends of extreme temperature indices are significant, but extreme precipitation indices are insignificant. Through the extreme temperature indices, the cold indices of extreme temperature decrease steadily and the warm indices of extreme temperature rise steadily, indicating that the trends of temperature rising in the basin are obvious and stable. In addition, indices of the extreme precipitation indicate that the consecutive dry days (CDD) decrease, the heavy precipitation days (R20) and the consecutive wet days (CWD) increase, and the annual total precipitation (PRCPTOT) increases steadily. The results have certain scientific value for climate change and a series of impacts brought by climate change in the Daqing River Basin. [ABSTRACT FROM AUTHOR]

The oxygen and hydrogen isotopic compositions (δ18O and δ2H) were measured on river water and precipitation collected from four sub-catchments within the upper Tuojiang River catchment. δ18O values of river water and precipitation exhibit significant seasonal variations. These seasonal variations are used for estimating the mean residence time (MRT) for four sub-catchments by an exponential model, ranging from 346 to 493 days. The correlation between catchment MRT and mean slope of the catchment (r2 = 0.29) is weak, while the correlations between catchment MRT, catchment area (r2 = 0.79) and topographic index (r2 = 0.98) are strong. These results indicate that topography and catchment area, both control the catchment MRT and the topographic index may be a reliable parameter for estimating the catchment MRT. Moreover, the relationship between land use types and MRT was investigated. The results show that paddy fields (r2 = 0.95) compared to the other land use types may have a greater impact on the MRT of the irrigation-dominated catchment. This study provides a preliminary exploration of the factors affecting MRT in the plain region and a basis for simulating MRT in the future. [ABSTRACT FROM AUTHOR]

Assessments of ecosystem service and function losses of wetlandscapes (i.e., wetlands and their hydrological catchments) suffer from knowledge gaps regarding impacts of ongoing hydro-climatic change. This study investigates hydro-climatic changes during 1976–2015 in 25 wetlandscapes distributed across the world's tropical, arid, temperate and cold climate zones. Results show that the wetlandscapes were subject to precipitation (P) and temperature (T) changes consistent with mean changes over the world's land area. However, arid and cold wetlandscapes experienced higher T increases than their respective climate zone. Also, average P decreased in arid and cold wetlandscapes, contrarily to P of arid and cold climate zones, suggesting that these wetlandscapes are located in regions of elevated climate pressures. For most wetlandscapes with available runoff (R) data, the decreases were larger in R than in P, which was attributed to aggravation of climate change impacts by enhanced evapotranspiration losses, e.g. caused by land-use changes. [ABSTRACT FROM AUTHOR]

The Hydrometeorological Sandbox - École de technologie supérieure (HYSETS) is a rich, comprehensive and large-scale database for hydrological modelling covering 14425 watersheds in North America. The database includes data covering the period 1950–2018 depending on the type and source of data. The data include a wide array of hydrometeorological data required to perform hydrological and climate change impact studies: (1) watershed properties including boundaries, area, elevation slope, land use and other physiographic information; (2) hydrometric gauging station discharge time-series; (3) precipitation, maximum and minimum daily air temperature time-series from weather station records and from (4) the SCDNA infilled gauge meteorological dataset; (5) the NRCan and Livneh gridded interpolated products' meteorological data; (6) ERA5 and ERA5-Land reanalysis data; and (7) the SNODAS and ERA5-Land snow water equivalent estimates. All data have been processed and averaged at the watershed scale, and provides a solid basis for hydrological modelling, climate change impact studies, model calibration assessment, regionalization method evaluation and essentially any study requiring access to large amounts of spatiotemporally varied hydrometeorological data. Measurement(s) elevation • temperature • hydrological precipitation process • Fluid Discharge • climate • physiographic feature Technology Type(s) digital curation Sample Characteristic - Environment watershed Sample Characteristic - Location North America Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.12600281 [ABSTRACT FROM AUTHOR]

A comprehensive assessment and bias corrections of two gridded daily precipitation products, based on gauge-only and multi-satellite observations, are undertaken in this study using independent rain gauge data in and around the Kabini River (KR) basin in South India. The KR basin, with complex terrain, highly variable precipitation and heterogeneous land use poses challenges in the development of accurate gridded precipitation products. The gauge-only gridded precipitation data from the India Meteorological Department (IMD) and multi-satellite gridded precipitation product from the Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA)-3B42 are evaluated at daily and monthly scales in this study. Both gridded precipitation products available at 0.25° spatial resolution are assessed using independent 57 rain gauge observations for the period of 2009–2016. Multiple visual and statistical metrics have been utilized to assess the error characteristics and capability of these gridded precipitation estimates in replicating extremes. Results indicate that gauge-only gridded product is generally better than the multi-satellite precipitation product. The multi-satellite product notably overestimates light precipitation and underestimates extreme precipitation over the study region. To mitigate the overestimation of dry days in the TMPA-3B42 estimates, a dry-day correction method is developed and is applied using nearby rain gauge observations. Furthermore, a quantile-based correction is also applied to both gridded precipitation products after confirming the stationarity of the data, which substantially improved both precipitation estimates for distributed hydrological modelling studies in the KR basin. [ABSTRACT FROM AUTHOR]

This study aims to model annual maximum precipitation based on extreme value theory for the Oued El Gourzi Watershed, Algeria. A generalized extreme value (GEV) distribution was used to determine the probability distribution of extreme values and their dependency on time for the five stations distributed across the watershed. The non-stationary models are used to represent the GEV parameters assumed an invariant shape parameter and linear functions as location and scale parameters. The best model was selected using Akaike's information criterion and Bayesian information criterion. Stationary and non-stationary return levels for different return periods have been proposed for the study area. [ABSTRACT FROM AUTHOR]

This study investigates the daily, monthly, and seasonal characteristics of precipitation and associated forcing processes for their spatial-temporal variations over two geographically distinct river basins (Kaligandaki and Koshi) in Nepal, located on the southern slopes of the central Himalayas. A 34-year (1981–2015) daily precipitation data set of 49 stations between the elevation ranges of 143 to 3870 m asl was used for this investigation. The Gini coefficient, and index, degree and period of precipitation concentrations, and rainfall gradients were derived to examine precipitation distribution characteristics and causes for their variation. A rapid decrease of rainfall with elevation was observed in the Kaligandaki basin throughout the period of record, while this pattern was reversed in the Koshi basin, due to the rain shadow and orographic effects, which is pronounced in the monsoon season. Mountain effects are likely responsible for the distinct differences in daily and monthly precipitation distribution, with irregular patterns observed in the northern region of Kaligandaki basin and southern region in Koshi basin, with uniform patterns in the southern region of Kaligandaki basin and the northern region of Koshi basin. There is also a distinct variation in seasonality, which is higher (concentrated over several months) in the central northern region in Kaligandaki basin and less concentrated in the northern region of Koshi basin. But monthly precipitation characteristics in the western portion of Koshi and the southern region of Kaligandaki basins show high variability and short concentration duration. However, the months when precipitation is concentrated differed between the basins: from late July to August in Kaligandaki and June to September in Koshi basin. This is because the monsoon arrives later in the west than in the eastern part of the country. Variation in number of rainy days is higher in Koshi, but rainfall amount is greatest in Kaligandaki basin due to its proximity to the ocean and the intense effect of the monsoon. In addition to its value for rainfall-induced disaster mitigation strategies and management planning, this study will be useful for hydrological modeling in these areas in the future. [ABSTRACT FROM AUTHOR]

This study assesses the high-resolution, 0.11° (12 km), Canadian Regional Climate Model Version 5 (CRCM5), interactively coupled to the one-dimensional Freshwater Lake model (FLake), to predict wintertime precipitation along the Canadian snowbelts of Lake Superior and Lake Huron. CRCM5–FLake was compared against various datasets to evaluate the 20-year (1995–2014) SWE and wintertime precipitation, seven lake-induced precipitation events and lake effect snowfall (LES) predictor variables during the months of December and January. The findings of SWE along both snowbelts in December and January show MBD ≤− 10 mm and ≤− 30 mm, respectively. Similarly, precipitation results along both snowbelts in December and January show MBD ≤− 5 mm and ≤− 10 mm, respectively. The negative biases in simulated SWE and precipitation, predominantly along the snowbelts, suggest that the model may un-realistically represent lake effect processes. Comparison of lake-induced precipitation events also indicates that the model mostly under-predicts the daily accumulated precipitation associated with each event but tends to accurately capture the timing and the general location of the squalls along the snowbelts, though not for highly localised snow bands. Furthermore, lake-wide results of LES predictor variables indicate that the model over-estimates lake surface temperature (LST) for both lakes during December and January and under-estimates ice cover concentrations for both lakes in December. The resultant biases could be attributed to limitations within the coupled RCM because the quality of reproducing lake-induced precipitation in this region is highly dependent on the performance of FLake. [ABSTRACT FROM AUTHOR]

Increase in human-induced climate warming is unequivocal and is subsequently causing an increase in the magnitude of precipitation extremes around the globe, inducing substantial damages to the socioeconomic sectors. Thus, a reliable projection of extreme precipitation scenarios is crucial for designing suitable adaptation strategies. At present, this is being attempted with the use of general circulation models (GCMs) projections. However, the GCMs simulate the extreme precipitation events rather poorly, especially over the tropical regions, and also suffer from frequent lack of reliability at local/regional scales. Therefore, it is of paramount significance to identify the relevant physical parameters for the extreme precipitation scenarios, and further implement these parameters in downscaling approaches to significantly improve the impact assessment at a regional scale. Previous studies have reported that the dynamic component (mainly vertical wind velocity) has a significant influence on the precipitation extremes over South Asian regions, along with the thermodynamic component. This indicates that the consideration of vertical wind velocity for projecting the precipitation extremes may significantly increase the efficacy of the downscaling approach, a contemplation that provoked its inclusion in statistical downscaling in this study. The methodology was demonstrated over the Mahanadi river basin (India), which often experiences heavy rainfall during the monsoon and post-monsoon disturbances originating from the Bay of Bengal (BoB). We observed that the dynamic component plays a crucial role in changing the pattern of precipitation extremes over the basin. Further, we noticed that inclusion of this dynamic component in statistical downscaling significantly improved the extreme precipitation projections. Based on these observations, we projected (2026–2055) the mean and extreme precipitation events, considering six most efficient CMIP5 models for the Indian subcontinent under RCP 4.5 and RCP 8.5 scenarios. The outcomes of this study can be utilized in deriving reliable water resource management practices. [ABSTRACT FROM AUTHOR]

Relationships between environmental variables associated with the spread of vector-borne pathogens, such as RNA viruses transmitted to humans and animals, remain poorly understood. Vesicular stomatitis (VS) is caused by a vector-borne, zoonotic RNA virus (VSV) and is the most common vesicular disease affecting livestock (domestic horses, cattle, pigs) throughout the Americas. This investigation focused on explaining patterns of more than 1500 VS-infected livestock premises in the western USA from 2004 to 2016 related to the ecology of the host-vector-virus-environment system. We investigated the relationship between VS incidents and habitat characteristics expected to be important to insect vectors: stream location, streamflow conditions, climate, and vegetation. Results show that VS incidents were distributed near the stream network with 72% located within 1 km of lotic habitat. Monthly incidents were closest to lotic habitat in April (x = 525 m) and furthest from lotic habitat in November, December and January (1843, 2141 and 4807 m) indicating that initial infection near streams may spread away from these locations. All first incidents (n = 35) occurred following peak annual streamflow, with 89% (31 of 35) of these occurring after streams returned to baseflow. This finding indicated that surveillance for VS could be targeted spatially in locally relevant geographic areas (that is, near streams) and temporally relative to local streamflow conditions which can be remotely monitored via existing web-accessible information networks. Habitat modeling of 11 subwatersheds revealed somewhat different models for each watershed with several factors important in multiple watersheds. In nine of the 11 watersheds, the highest model PC (31-71%) represented either higher-than-average long-term mean temperature or lower-than-average long-term mean precipitation. Approaching habitat modeling on a watershed basis reveals information to support additional research. These spatial and temporal relationships showcase the importance of hydrologic contributions to the emergence and distribution of an arthropod-borne disease in the western USA. [ABSTRACT FROM AUTHOR]

The climate of the circumpolar Boreal forest is changing rapidly, resulting in a growing frequency of wildfires and changing precipitation patterns. These climate-related stressors may influence the cycling of nutrients within, and overall ecosystem condition of, Boreal watersheds. However, long-term perspectives of concurrent climate-related impacts on the cycling of nutrients in watersheds are rare. We present multi-decadal terrestrial and lake mass budgets of nitrogen, phosphorus and carbon within a headwater Boreal Shield watershed that was recovering from an extensive wildfire while experiencing measureable increases in annual precipitation. We used these budgets to quantify associations between nutrient retention in each ecosystem and changes in metrics defining landscape recovery after wildfire or precipitation. The terrestrial watershed retained over half of all nitrogen and phosphorus delivered to it by the atmosphere. Strong nutrient retention occurred despite ongoing landscape recovery from wildfire, measurable increases in precipitation, a forest tent caterpillar defoliation and rising atmospheric deposition. A downstream headwater lake was also a strong and consistent sink of nitrogen and phosphorus, highlighting a whole-watershed resistance to environmental disturbances. However, carbon was strongly lost downstream from the terrestrial ecosystem in close and positive association with precipitation, resulting in a darkening of the headwater lake over time with implications for the functioning of its ecosystem. Long-term mass budget monitoring of a Boreal catchment has provided insight into the resistances and dynamic changes within a northern watershed exposed to concurrent wildfire and increasing precipitation conditions. [ABSTRACT FROM AUTHOR]

There is a well-known seesaw pattern of precipitation between the tropical western North Pacific (WNP) and the Yangtze River basin (YRB) during summer. This study identified that this out-of-phase relationship experiences a subseasonal change; that is, the relationship is strong during early summer but much weaker during mid-summer. We investigated the large-scale circulation anomalies responsible for the YRB rainfall anomalies on the subseasonal timescale. It was found that the YRB rainfall is mainly affected by the tropical circulation anomalies during early summer, i.e., the anticyclonic or cyclonic anomaly over the subtropical WNP associated with the precipitation anomalies over the tropical WNP. During mid-summer, the YRB rainfall is mainly affected by the extratropical circulation anomalies in both the lower and upper troposphere. In the lower troposphere, the northeasterly anomaly north of the YRB favors heavier rainfall over the YRB by intensifying the meridional gradient of the equivalent potential temperature over the YRB. In the upper troposphere, the meridional displacement of the Asian westerly jet and the zonally oriented teleconnection pattern along the jet also affect the YRB rainfall. The subseasonal change in the WNP-YRB precipitation relationship illustrated by this study has important implications for the subseasonalto- seasonal forecasting of the YRB rainfall. [ABSTRACT FROM AUTHOR]

Located in northern Quebec, Canada, eight hydroelectric reservoirs of a 9782-km2 maximal area cover 6.4% of the La Grande watershed. This study investigates the changes brought by the impoundment of these reservoirs on seasonal climate and precipitation recycling. Two 30-year climate simulations, corresponding to pre- and post-impoundment conditions, were used. They were generated with the fifth-generation Canadian Regional Climate Model (CRCM5), fully coupled to a 1D lake model (FLake). Seasonal temperatures and annual energy budget were generally well reproduced by the model, except in spring when a cold bias, probably related to the overestimation of snow cover, was seen. The difference in 2-m temperature shows that reservoirs induce localized warming in winter (+0.7 ± 0.02 °C) and cooling in the summer (−0.3 ± 0.02 °C). The available energy at the surface increases throughout the year, mostly due to a decrease in surface albedo. Fall latent and sensible heat fluxes are enhanced due to additional energy storage and availability in summer and spring. The changes in precipitation and runoff are within the model internal variability. At the watershed scale, reservoirs induce an additional evaporation of only 5.9 mm year−1 (2%). We use Brubaker’s precipitation recycling model to estimate how much of the precipitation is recycled within the watershed. In both simulations, the maximal precipitation recycling occurs in July (less than 6%), indicating weak land-atmosphere coupling. Reservoirs do not seem to affect this coupling, as precipitation recycling only decreased by 0.6% in July. [ABSTRACT FROM AUTHOR]

To support the GPM mission which is homologous to its predecessor, the Tropical Rainfall Measuring Mission (TRMM), this study has been undertaken to evaluate the accuracy of Tropical Rainfall Measuring Mission multi-satellite precipitation analysis (TMPA) daily-accumulated precipitation products for 5 years (2008-2012) using the statistical methods and contingency table method. The analysis was performed on daily, monthly, seasonal and yearly basis. The TMPA precipitation estimates were also evaluated for each grid point i.e. 0.25° × 0.25° and for 18 rain gauge stations of the Betwa River basin, India. Results indicated that TMPA precipitation overestimates the daily and monthly precipitation in general, particularly for the middle sub-basin in the non-monsoon season. Furthermore, precision of TMPA precipitation estimates declines with the decrease of altitude at both grid and sub-basin scale. The study also revealed that TMPA precipitation estimates provide better accuracy in the upstream of the basin compared to downstream basin. Nevertheless, the detection capability of daily TMPA precipitation improves with increase in altitude for drizzle rain events. However, the detection capability decreases during non-monsoon and monsoon seasons when capturing moderate and heavy rain events, respectively. The veracity of TMPA precipitation estimates was improved during the rainy season than during the dry season at all scenarios investigated. The analyses suggest that there is a need for better precipitation estimation algorithm and extensive accuracy verification against terrestrial precipitation measurement to capture the different types of rain events more reliably over the sub-humid tropical regions of India. [ABSTRACT FROM AUTHOR]

Climate change has become an important issue for scientific community, for its numerous impacts, especially on agriculture and environment. To shed light on this phenomenon, long data-sets of meteorological data as well as temperature and rainfall extreme events are needed, since they are important climate variability indicators. In a small semi-agricultural catchment of the Italian Apennines, drained by the Centonara Stream, weather data have been monitored for 30 years (1986-2015). Here, their trend was identified with Mann-Kendall test, and the temperature and precipitation extremes were characterized by means of specific indices. Data were analyzed at event, daily, seasonal, and annual bases. In addition, to understand implications of rainfall patterns on catchment hydrological response, a total of 388 rainfall-streamflow events (recorded during 1994-2009) were analyzed. Results showed a significant increase of temperature (minimum (Tn), mean (Tm), and maximum (Tx)), both at annual and seasonal base, except for Winter, with an annual mean increase of 0.08, 0.09, and 0.13 °C year for Tn, Tm, and Tx, respectively. Annual rainfall data showed a positive trend for the number of wet days, but not in the quantity. In Winter, the rainfall amount and the number of wet days increased. The annual number of rainfall extreme events ( P > 20.2 mm and D > 18.3 h) significantly increased, especially in spring and autumn. The rainfall-streamflow relationship suggested that the flow response of the Centonara Stream depends mainly on the rainfall amount. So, since the number of extreme events ( P > 20.2 mm) is increasing in spring and autumn, an increase of events with high streamflow in these seasons may occur. [ABSTRACT FROM AUTHOR]

This study analyzes the impact of anthropogenic climate change in the hydroclimatology of Senegal with a focus over the lake of Guiers basin for the middle (2041-2060) and late twenty-first century (2080-2099). To this end, high-resolution multimodel ensemble based on regional climate model experiments considering two Representative Concentration Pathways (RCP4.5 and RCP8.5) is used. The results indicate that an elevated warming, leading to substantial increase of atmospheric water demand, is projected over the whole of Senegal. In the Lake basin, these increases in potential evapotranspiration (PE) range between 10 and 25 % in the near future and for RCP4.5 while for the far future and RCP8.5, they exceed 50 %. In addition, mean precipitation unveils contrasting changes with wetter (10 to 25 % more) conditions by the middle of the century and drier conditions (more than 50 %) during the late twenty-first century. Such changes cause more/less evapotranspiration and soil moisture respectively during the two future periods. Furthermore, surface runoff shows a tendency to increase in most areas amid few locations including the Lake basin with substantial reduction. Finally, it is found that while semi-arid climates develop in the RCP4.5 scenario, generalized arid conditions prevail over the whole Senegal for RCP8.5. It is thus evident that these future climate conditions substantially threaten freshwater availability for the country and irrigated cropping over the Lake basin. Therefore, strong governmental politics are needed to help design response options to cope with the challenges posed by the projected climate change for the country. [ABSTRACT FROM AUTHOR]

Hydrology cycle of river basins and available water resources in arid and semi-arid regions are highly affected by climate changes. In recent years, the increment of temperature due to excessive increased emission of greenhouse gases has led to an abnormality in the climate system of the earth. The main objective of this study is to survey the future climate changes in one of the biggest mountainous watersheds in northeast of Iran (i.e., Kashafrood). In this research, by considering the precipitation and temperature as two important climatic parameters in watersheds, 14 models evolved in the general circulation models (GCMs) of the newest generation in the Coupled Model Intercomparison Project Phase 5 (CMIP5) were used to forecast the future climate changes in the study area. For the historical period of 1992-2005, four evaluation criteria including Nash-Sutcliffe (NS), percent of bias (PBIAS), coefficient of determination ( R ) and the ratio of the root-mean-square-error to the standard deviation of measured data (RSR) were used to compare the simulated observed data for assessing goodness-of-fit of the models. In the primary results, four climate models namely GFDL-ESM2G, IPSL-CM5A-MR, MIROC-ESM, and NorESM1-M were selected among the abovementioned 14 models due to their more prediction accuracies to the investigated evaluation criteria. Thereafter, climate changes of the future periods (near-century, 2006-2037; mid-century, 2037-2070; and late-century, 2070-2100) were investigated and compared by four representative concentration pathways (RCPs) of new emission scenarios of RCP2.6, RCP4.5, RCP6.0, and RCP8.5. In order to assess the trend of annual and seasonal changes of climatic components, Mann-Kendall non-parametric test (MK) was also employed. The results of Mann-Kendall test revealed that the precipitation has significant variable trends of both positive and negative alterations. Furthermore, the mean, maximum, and minimum temperature values had significant positive trends at 90, 99, and 99.9 % confidence level. On the other hand, in all parts of the Kashafrood Watershed (KW), the average temperature of watershed will be increased up to 0.56-3.3 °C and the mean precipitation will be decreased up to 10.7 % by the end of the twenty-first century comparing to the historical baselines. Also, in seasonal scale, the maximum and minimum precipitations will occur in spring and summer, respectively, and the mean temperature is higher than the historical baseline in all seasons. The maximum and minimum values of the mean temperature will occur in summer and winter, respectively, and the amount of seasonal precipitation in these seasons will be reduced. [ABSTRACT FROM AUTHOR]

A long-term simulation for the period 1990-2010 is conducted with the latest version of the International Centre for Theoretical Physics' Regional Climate Model (RegCM4), driven by ERA-Interim boundary conditions at a grid spacing of 25 km. The Community Land Model (CLM) is used to describe land surface processes, with updates in the surface parameters, including the land cover and surface emissivity. The simulation is compared against observations to evaluate the model performance in reproducing the present day climatology and interannual variability over the 10 main river basins in China, with focus on surface air temperature and precipitation. Temperature and precipitation from the ERA-Interim reanalysis are also considered in the model assessment. Results show that the model reproduces the present day climatology over China and its main river basins, with better performances in June-July-August compared to December-January-February (DJF). In DJF, we find a warm bias at high latitudes, underestimated precipitation in the south, and overestimated precipitation in the north. The model in general captures the observed interannual variability, with greater skill for temperature. We also find an underestimation of heavy precipitation events in eastern China, and an underestimation of consecutive dry days in northern China and the Tibetan Plateau. Similar biases for both mean climatology and extremes are found in the ERA-Interim reanalysis, indicating the difficulties for climate models in simulating extreme monsoon climate events over East Asia. [ABSTRACT FROM AUTHOR]

Tigris and Euphrates river basin (TERB) is one of the largest river basins in the Middle East, and the precipitation (in the form of snowfall) is a major source of streamflow. This study investigates the spatial and temporal variability of precipitation and streamflow in TERB to better understand the hydroclimatic variables and how they varied over time. The precipitation shows a decreasing trend with 1980s being wetter and 2000s being drier. A total of 55 and 40% reduction in high flows in Tigris and Euphrates rivers at T20 and E3 was seen in post-reservoir period. A lag time of 3 to 4 and 5 to 6 months was estimated between peak snowfall and runoff time periods. Decreasing precipitation and streamflow along with several planned dams could hamper the sustainability of several Mesopotamian marshlands that completely depend on the water from the Tigris and Euphrates rivers. [ABSTRACT FROM AUTHOR]

The change structures of precipitation and precipitation intensity and rainy days are analyzed for the Pearl River Basin (from 1959 to 2009) on the basis of a suite of 24 climatic indices derived from daily precipitation data at 62 meteorological stations with the help of the Mann-Kendall test. Contributions of seasonal precipitation and precipitation intensity class to the annual precipitation are also examined using the inverse distance weighted method. The following four conclusions can be drawn: (1) although the average annual precipitation of the entire basin does not show obvious variation, the number of annual rainy days has decreased significantly in 98.3 % of the stations. These two factors result in an obvious increase in precipitation intensity at 64.5 % of the stations. (2) No clear change trend has been found for seasonal precipitation over the entire area; however, the number of rainy days in each season has decreased significantly. In particular, the number of rainy days in the entire year and in the fall season has decreased in 98.3 and 100 % of the stations, respectively. (3) Although the number of rainy days in drizzle has decreased in 83.9 % of the stations, the number of rainy days where heavy rain and extremely heavy rain occurred increased in nearly 75.8 and 82.3 % of the stations, respectively. (4) The number of rainy days in fall and winter contributes more to the change in the number of annual rainy days than the number of rainy days in spring and summer. Heavy rain and extremely heavy rain contribute more to the change in total annual precipitation than drizzle; however, they contribute less to the change in the number of annual rainy days than drizzle. The findings in this study can provide important information for formulating water resource and eco-environment management strategies in the Pearl River Basin to policymakers and stakeholders. [ABSTRACT FROM AUTHOR]

As the largest component of the global water cycle, precipitation plays a critical role in determining available water in the terrestrial ecosystems. Numerous precipitation products have been generated during the last decades, but they differ substantially in terms of their spatial and temporal variations. In this study, we compared seven precipitation products covering ten major river basins of China from 1980 to 2007 and found large differences among the products. Overall, the Global Precipitation Climatology Center (GPCC) product shows the highest correlation with rain gauge measurements and lowest estimation errors over the ten basins. The performances of other products also clearly differ over the ten basins, and the maximum estimates were 1.27 ± 0.21 times the minimum estimates in terms of interannual variability in precipitation. Based on the seven products, we generated a new precipitation dataset using the Bayesian model averaging method. Compared with all the individual products, the new dataset indicates the decreased root mean square error and increased coefficient of correlation. In the statistical analysis of the weight for each of the products, the GPCC product contributed the maximum weight among almost all river basins. Both the ERA-Interim and MERRA products contributed the minimum weights, being less than 10 %. Our results highlight the need to investigate and improve the performance of precipitation products when evaluating the regional water balance. [ABSTRACT FROM AUTHOR]

For 50 years of long observation period (1960-2009), on a high level of statistical significance (95 %), a decreasing trend of annual precipitation amounts and an increasing trend of the number of rainy days during the year (64 %) were found. For the seasonal changes (V-X), similarly, there was found a statistically significant (94 %) decreasing precipitation amount trend and an increasing trend of the number of rainy days (50 %). As far as the intensity of maximum precipitation is concerned, a very statistically significant increasing trend (95 %) was found. Taking as the basis, the model for a trend, defined for the period of 1960-2009, the increase of weighted average interval values of maximum precipitation amounts ( h ≥ 0.75 t) in the year 2059 was estimated to be about 26 %, in comparison with the starting year 1960. An increasing trend of maximum precipitation frequency in Wrocław was also proved. To a safe sewerage systems designing in Wrocław according to current standards (EN 752 ; DWA-A118 ), the precipitation frequency to the simulations of excessive accumulation occurrences to the land level should be changed. [ABSTRACT FROM AUTHOR]

The main purpose of this study is to evaluate the impacts of climate change on Izmir-Tahtali freshwater basin, which is located in the Aegean Region of Turkey. For this purpose, a developed strategy involving statistical downscaling and hydrological modeling is illustrated through its application to the basin. Prior to statistical downscaling of precipitation and temperature, the explanatory variables are obtained from National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis data set. All possible regression approach is used to establish the most parsimonious relationship between precipitation, temperature, and climatic variables. Selected predictors have been used in training of artificial neural networks-based downscaling models and the trained models with the obtained relationships have been operated to produce scenario precipitation and temperature from the simulations of third Generation Coupled Climate Model. Biases from downscaled outputs have been reduced after downscaling process. Finally, the corrected downscaled outputs have been transformed to runoff by means of a monthly parametric hydrological model GR2M to assess the probable impacts of temperature and precipitation changes on runoff. According to the A1B climate scenario results, statistically significant trends are foreseen for precipitation, temperature, and runoff in the study basin. [ABSTRACT FROM AUTHOR]

Regional frequency analysis and spatial-temporal patterns of precipitation extremes are investigated based on daily precipitation data covering 1960-2009 using the index-flood L-moments method together with some advanced statistical tests and spatial analysis techniques. The results indicate that: (1) the entire Yangtze River basin can be divided into six homogeneous regions in terms of extreme daily precipitation index. Goodness-of-fit test indicates that Pearson type III (PE3, three parameters), general extreme-value (GEV, three parameters), and general normal (GNO, three parameters) perform well in fitting regional precipitation extremes; (2) the regional growth curves for each homogeneous region with 99 % error bands show that the quantile estimates are reliable enough and can be used when return periods are less than 100 years, and the results indicate that extreme precipitation events are highly probable to occur in regions V and VI, and hence higher risk of floods and droughts; and (3) spatial patterns of annual extreme daily precipitation with return period of 20 years indicate that precipitation amount increases gradually from the upper to the lower Yangtze River basin, showing higher risks of floods and droughts in the middle and lower Yangtze River basin, and this result is in good agreement with those derived from regional growth curves. [ABSTRACT FROM AUTHOR]

This study analyzed the inter- and inner-annual variations of discharge regimes in the upper and mid reaches of the Heihe River basin. These variations then correlated with temperature and precipitation variations in the area. The differences between the runoff regimes at the upper and mid reaches were compared, and the human impacts on discharge variations in the Heihe River were discussed. The results indicate that in the upper reaches, the long-term trends and periods of discharge and precipitation correlate well. In the mid reaches, the discharge and temperature trends correlate well, and the short discharge and precipitation periods correlate well. Precipitation increases would generate more runoff in both the upper and mid reaches, but the effects of temperature increases on discharge are different in the upper and mid reaches. Temperature increases would enhance the glacial ablation processes and increase runoff in the upper reaches. However, temperature increases would increase the evaporation and decrease runoff in the mid reaches. After the 1980s, higher temperature enhanced snow and glacial melt, and increasing precipitation increased the discharge in the upper reaches. Although increasing precipitation increased some discharge, great human activities caused a notable discharge decrease in the 1990s in the mid reaches, especially during the spring to autumn when large amounts of water resources were used for irrigation. In summary, both precipitation and temperature impact the availability of water resources in the study area, and active and effective adaptation strategies should be developed to improve the efficiency of water resource exploration and to prevent the desertification processes in the arid Heihe River basin. [ABSTRACT FROM AUTHOR]

Much attention has recently been focused on the effects that climate variability and human activities have had on runoff. In this study, data from the Kaidu River Basin in the arid region of northwest China were analyzed to investigate changes in annual runoff during the period of 1960-2009. The nonparametric Mann-Kendall test and the Mann-Kendall-Sneyers test were used to identify trend and step change point in the annual runoff. It was found that the basin had a significant increasing trend in annual runoff. Step change point in annual runoff was identified in the basin, which occurred in the year around 1993 dividing the long-term runoff series into a natural period (1960-1993) and a human-induced period (1994-2009). Then, the hydrologic sensitivity analysis method was employed to evaluate the effects of climate variability and human activities on mean annual runoff for the human-induced period based on precipitation and potential evapotranspiration. In 1994-2009, climate variability was the main factor that increased runoff with contribution of 90.5 %, while the increasing percentage due to human activities only accounted for 9.5 %, showing that runoff in the Kaidu River Basin is more sensitive to climate variability than human activities. This study quantitatively distinguishes the effects between climate variability and human activities on runoff, which can do duty for a reference for regional water resources assessment and management. [ABSTRACT FROM AUTHOR]

Long-term data on precipitation and runoff are essential to draw firm conclusions about the behavior and trends of hydrological catchments that may be influenced by land use and climate change. Here the longest continuous runoff records from small catchments (<1 km) in Switzerland (and possibly worldwide) are reported. The history of the hydrological monitoring in the Sperbel- and Rappengraben (Emmental) is summarized, and inherent uncertainties in the data arising from the operation of the gauges are described. The runoff stations operated safely for more than 90% of the summer months when most of the major flood events occurred. Nevertheless, the absolute values of peak runoff during the largest flood events are subject to considerable uncertainty. The observed differences in average, base, and peak runoff can only partly be attributed to the substantial differences in forest coverage. This treasure trove of data can be used in various ways, exemplified here with an analysis of the generalized extreme value distributions of the two catchments. These distributions, and hence flood return periods, have varied greatly in the course of one century, influenced by the occurrence of single extreme events. The data will be made publicly available for the further analysis of the mechanisms governing the runoff behavior of small catchments, as well as for testing stochastic and deterministic models. [ABSTRACT FROM AUTHOR]

We investigated the moisture origin and contribution of different water sources to surface runoff entering the headwaters of the Heihe River basin on the basis of NECP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) re-analysis data and variations in the stable hydrogen and oxygen isotope ratios (δD and δ18O) of precipitation, spring, river, and melt water. The similar seasonality in precipitation δ18O at different sites reveals the same moisture origin for water entering the headwaters of the Heihe River basin. The similarity in the seasonality of δ18O and d-excess for precipitation at Yeniugou and Urumchi, which showed more positive δ18O and lower d-excess values in summer and more negative δ18O and higher d-excess values in winter, indicates a dominant effect of westerly air masses in summer and the integrated influence of westerly and polar air masses in winter. Higher d-excess values throughout the year for Yeniugou suggest that in arid inland areas 18 of northwestern China, water is intensively recycled. Temporal changes in δ18O, δD, and d-excess reveal distinct contributions of different bodies of water to surface runoff. For example, there were similar trends for δD, δ18O, and d-excess of precipitation and river water from June to September, similar δ18O trends for river and spring water from December to February, and similar trends for precipitation and runoff volumes. However, there were significant differences in δ18O between melt water and river water in September. Our results show that the recharge of surface runoff by precipitation occurred mainly from June to mid-September, whereas the supply of surface runoff in winter was from base flow (as spring water), mostly with a lower runoff amount. [ABSTRACT FROM AUTHOR]

The article discusses the water supply shortage in India as its population continues to boom. Water pollution is just one of the many problems that India is facing, more to this is the availability of water where the city of Delhi is the forerunner of this looming water crisis. India consider it an ambitious plan to connect the majority of its river basins through a vast network of canals, diverting billions of litres from the more water-rich river basins to those with less. Although it is unclear whether the solution is effective, the logic behind such plan is to capture the surplus water that flows wastefully to the sea which resulted from the variable distribution of precipitation.

The climate of Atndalen Valley is described by data collected by the standard network of stations currently run by the Norwegian Meteorological institute. It consists of one weather station (Sørneset) with full instrumental equipment, and three precipitation stations with a reduced set of equipment. At the latter stations, precipitation, snow depth, and snow cover are observed. Most of the stations, including the weather station, are situated in the central part of the watershed, near Atnsjøen. The climate of the Atndalen is of a continental type with precipitation minimum in late winter or spring and maximum during summer. The mean annual precipitation is about 500 mm near Atnsjøen (701 m a.s.l.) for the 30 year normal period 1961–1990. At the meteorological station Sørneset the warmest month is July, 11.2 °C, while the coldest month is January, -9.9 °C, i.e. an annual amplitude of 21.1 °C. The mean cloud cover varies from 4.5 oktas in February to 5.4 oktas in July, September and October. The highest ratio of relative sunshine is about 50% in spring. The mean snow depth increases during winter and early spring and reaches its maximum of 68 cm in March. The snow cover disappears on 9 May ±12 days and establishes on 5 November ±18 days. Variations in precipitation (since 1904) and temperature (since 1864) were studied on a decadal time scale by Gaussian filtering technique, and the significance of trends on the 0.05 level were studied by the Mann–Kendall test. For the whole period no significant trend in annual precipitation was detected. The maximum value was located to the 1920s and the minimum value to the 1910s. Annual mean temperature has increased significantly since 1864, and the classical temperature optimum in the 1930s was surpassed in the 1990s. By adopting a sinus model including the first Fourier component, trends and variations in climatological periods as well as heat and frost sums were studied. The frost free period has since 1864 increased by 13 days within 100 years based on a linear trend line. Earlier passing dates in spring largely account for the increase. The length of the growth season also increased up to about 1950. The annual heat sum shows a linear increase of about 103 daydegrees per 100 years while the annual frost sum varies considerably from period to period and fitted badly with a linear model. [ABSTRACT FROM AUTHOR]

The hydrological investigations in the Atna basin started in 1917 with discharge measurements at the outlet of Lake Atnsjøen. Ice data are available from the lake since 1950 and water temperature data from 1980. With the start of the FORSKREF program in 1986 the number of hydrological stations increased substantially and included also snow measurements. During the FORSKREF period 1986–98 the annual mean discharge was 8% lower than during the normal period 1931–60. The annual flood is highest during the snow melt in spring, an exception was 1987 when a rain flood in October was the annual high. The spring flood in early June 1995 was the largest ever recorded and had a 100–200 year return period. The water temperature is low above tree-line at 1000 m a. s. l., rarely exceeding 7–8 °C. The temperature increases gradually with decreasing altitude and is periodically above 15 °C at 400 m a. s. l. The Atna Lake is an important heat source for the river downstream. In this lake, wind mixing normally prevents the development of a strong summer thermocline. The lake usually freezes over in late November and has a stable ice cover of 50–90 cm thickness in early spring. The ice normally breaks up in late May; thus the mean ice-covered period is 6 months. The ice cover on the river is less stable and rather large ice-runs are common on the lower part of River Atna. The snow measurements are carried out in April in a small subbasin between 800 and 1200 m a. s. l. The snow cover is unevenly distributed due to strong wind transport, but the pattern is more or less the same from one season to another. The mean snow accumulation in this basin is equivalent to 205 mm of precipitation. [ABSTRACT FROM AUTHOR]

In hydrology, evapotranspiration (ET) is defined as phase conversion and rise of water in soils, plants, rivers, lakes, and seas under the atmospheric conditions. Investigation of water displacement through either ET or precipitations, runoffs and infiltrations may provide significant contributions for water resources management practices. In this study, daily, monthly, and seasonal ET maps were generated for Minöz Stream Watershed of Kavak town of Samsun province with the aid of energy balance-based METRIC model for the water-year of 2007. Resultant ET maps were assessed through vegetation covers, land use patterns, actual precipitations, and runoff parameters. In a previous study carried out over the same watershed, amount of water to be converted into ET was calculated as 517.0 mm for water-year of 2007. In present study, total ET for the relevant period of the same watershed was estimated as 610.0 mm. Estimated ET value was slightly greater than the total quantity of water to be converted into ET. Present ET maps were also well complied with the land use patterns. [ABSTRACT FROM AUTHOR]