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Based on numerical weather prediction model Weather Research and Forecasting (WRF) and Hydrologic Modeling System (HEC-HMS), a coupling model is constructed in Taihang Piedmont basin. The WRF model parameter scheme combinations composed of microphysics, planetary boundary layers, and cumulus parameterizations suitable for the study area are optimized. In both time and space, we tested the effects of the WRF model by a multi-index evaluation system composed of relative error, root meantime square error, probability of detection, false alarm ratio, and critical success index and established this system in two stages. A multi-attribute decision-making model based on Technique for Order Preference by Similarity to an Ideal Solution and grey correlation degree is proposed to optimize each parameter scheme. Among 18 parameter scheme combinations, Mellor-Yamada-Janjic, Grell-Devinji, Purdue-Lin, Betts-Miller-Janjić, and Single-Moment6 are ideal choices according to the simulation performance in both time and space. Using the unidirectional coupling method, the rolling rainfall forecast results of the WRF model in the 24 h and 48 h forecast periods are input to HEC-HMS hydrological model to simulate three typical floods. The coupling simulation results are better than the traditional forecast method, and it prolongs the flood forecast period of the Taihang Piedmont basin. [ABSTRACT FROM AUTHOR]

Flood simulation in sub-humid regions is one of the difficult issues in hydrology. Liulin experimental watershed, a typical sub-humid region in northern China, was selected for flood simulation. 20 rainfall–runoff events from 1995 to 2021 were selected to calibrate and validate the sub-distributed HEC-HMS model. The applicability of the model to flood simulation in the Liulin experimental watershed was explored. The influences of different runoff generation methods (SCS-CN method and initial constant method) and simulation time steps (1 h and 30 min) on flood simulation were compared. The applicability of the model to different antecedent moisture conditions and different flood characteristics was also analyzed. The results showed that all the schemes of rainfall–runoff models with different runoff generation methods and time steps have satisfactory performance in simulating floods. When the time step is 1 h, the initial constant runoff generation method was more suitable for runoff simulation, however, when the time step is 30 min, the SCS-CN runoff generation method was more robust. As the simulation time step decreased, the model performance was improved, but the improvement amplitude was greater when the SCS-CN method was used. In addition, the model performed better when antecedent moisture was higher, and the flood was single-peak. When the measured peak discharge was lower than 100 m3/s, the model could simulate the peak discharge and peak time better, and conversely, the model could simulate the flood volume and flood hydrograph better. This study is valuable for flood forecasting in sub-humid areas. [ABSTRACT FROM AUTHOR]

The spatial distribution and depth of precipitation are the main driving factors for the formation of flood disasters. Precipitation nowcasting plays a crucial role in rainstorm warning, flood mitigation and water resources management. However, high spatiotemporal resolution nowcasting is very challenging owing to the uncertain dynamics and chaos, especially at a small-scale region. In recent years, deep learning approaches were applied in precipitation nowcasting and achieved good performance in learning spatiotemporal features. In this paper, ConvLSTM model and sequences of radar reflectivity maps were used to forecast the future sequence of reflectivity maps with up to 2 h lead time in Liulin watershed with a small area of 57.4 km2. Dynamic hierarchical Z–I relationship was employed to calculate the forecasting precipitation and the forecasted spatiotemporal features were compared to the observed. The results indicated that the model can provide a well performance for the reflectivity above 10 dBZ with 0.70 of CSI for 30 min nowcasting and 0.57 for 2 h nowcasting, but was not good at forecasting the reflectivity above 30 dBZ with 0.38 of mean CSI for 30 min nowcasting and 0.12 for 2 h nowcasting, which have a decrease of 45.7% and 78.9%, respectively. The forecasted precipitation could truly show the details of precipitation spatial distribution and provide the accuracy of forecasting area with 49.2% for 30 min nowcasting. The satisfied areal precipitation depth could be offered basically with 26.3% of Bias for 30 min nowcasting in Liulin watershed. [ABSTRACT FROM AUTHOR]

Low-impact development (LID) facilities constitute an important element of sponge cities. In this paper, a system of siting suitability indicators was established for green roofs, permeable pavement and rain gardens. Based on the ArcGIS superposition analysis tool, the suitable area and area upper limit of LID facilities in each subcatchment were determined. Nonlinear functions of the LID deployment area and various rainfall characteristics were constructed using a multilayer perceptron (MLP) as a surrogate model. The results showed that (1) the upper limit of the suitable area for green roof deployment in each subcatchment ranged from 5.46% to 22.87%. The upper limit of the suitable area for permeable pavement application varied between 8.31% and 23.65%. The upper limit of the suitable area for rain garden deployment varied between 18.12% and 36.95%; (2) a final LID facility layout scheme was selected at a total outflow of 10,700 m3, peak discharge of 3.49 m3/s and total investment of 0.76 billion yuan during the construction and management period; (3) the total outflow reduction rate under the LID model ranged from 32.15% to 40.29%, and the peak discharge reduction rate ranged from 17.93% to 36.20%; (4) the computation time of the surrogate optimization model could be reduced to 0.37% of that of Storm Water Management Model (SWMM) conventional numerical optimisation. Herein, the surrogate model can be used to determine the optimal solution for the LID facility placement area assuming fixed reduction amounts of the outflow and peak discharge. [ABSTRACT FROM AUTHOR]

In flash flood events, predicting the impact loads of rushing water is helpful to detect the possible and direct damage to the downstream structures. The present study conducted three-dimensional numerical simulations for three typical laboratory experiments with emphasis on the hydrodynamic impact. Two RANS-based k-ε models and the LES model were chosen for the turbulence closure. The VOF method was applied to track the free surface. The numerical model provided satisfactory results of the temporal variations of both water depth and hydrodynamic load, which are in great agreement with the experimental data. Further quantitative comparisons also show that the deviations between simulations and experiments are small. The values of performance indicators mean-absolute deviation (MAD), root-mean-squared deviation (RMSD) and mean-absolute percentage deviation (MAPD) are respectively lower than 0.05 (0.03 m), 0.08 (0.048 m) and 19% for depth prediction, lower than 0.05 (0.03 kPa), 0.11 (0.06 kPa) and 11% for pressure prediction, and lower than 0.7 N, 1N and 15% for net force prediction. The absolute values of relative percent deviation (RPD) are less than 27% and 25% for the prediction of peak pressure and peak net force, respectively. The values of Nash–Sutcliffe efficiency (NSE) for depth and pressure are higher than 0.8. Moreover, the impulse of pressure or net force exhibits better predictability than its instantaneous values. Additional investigation shows that the time-varying behaviour of the impact force are significantly affected by the upstream initial depth, and the maximum impact force has a quadratic relationship with the initial depth. [ABSTRACT FROM AUTHOR]

Adopting new technologies to calibrate hydrological models to produce good simulations for water resources or flood risk management is one of the important research topics in hydrology field. Incorporating hydrological signatures and concepts in hydrological model calibration becomes prevalent in recent years. A good realistic simulation of hydrological processes within the catchment is more significant than only achieving good performance at watershed outlet with single-statistical-objective function. This research adopts the concept of flood scaling property, which describes the statistical relationship between flood peak, its contributing areas and additional catchment attributes, to behave as one of the constraints under multi-objective model calibration framework. Several designed calibration scenarios are tested by employing the soil and water assessment tool hydrological model. In comparison with single-objective calibration scenarios, multi-objective calibration method is recommended to obtain both good simulation at catchment outlet and sub-basins reaches. The multi-objective calibration method assists in improving the model performance in terms of flow duration curve and also in reducing the bias of long-term runoff ratio. The proposed model calibration approach reflects the hydrological interaction of flood peaks across sub-basins and takes into account the catchment antecedent wetness and climatic condition for each flood event. [ABSTRACT FROM AUTHOR]

Hydrological models are a conceptual representation of a simplified hydrological cycle. The hydrological cycle is the water cycle that circulates water from the land surface to the atmosphere and back again to the land. With the use of Hydrologic Engineering Center-Hydrologic Modeling System (HEC-HMS), an event-based model and a continous hydrological model were established in Zijinguan watershed of Daqinghe River basin. To study the loss methods provided by HEC-HMS and its appropriateness for model fitting, is the main objective of this paper. The watershed was delineated with HEC-GeoHMS in ArcGIS, and its properties were extracted from a Digital Elevation Model (DEM) of 30 m × 30 m. The HEC-HMS includes a soil conservation service curve number (SCS-CN) method and a soil moisture calculation (SMA) loss method, simulating the event and continuous runoff, respectively. SCS Unit hydrograph and Muskingum were used for flow routing. Specifically, eight rainfall events were selected for calibrating (6 events) and verifying (2 events) the event-based model. Similarly, for the continuous model the wet seasons of eight different years were used for calibration and verification. The calibrated parameters of the events model were used in the continuous model. The soil moisture and evapotranspiration data were decoded from the satellite data to set in the continuous model. The performance of SCS-CN and SMA models was compared. During the calibration period, the values of NSE, PEV and PEPF range from 0.605 to 0.744, 3.1 to 13.58%, and 11.104 to 27.72%, and during validation they are 0.527 to 0.634, 4.35% to 5.01%, and 13.66% to 27.88%, for SCS-CN model. For the SMA model, the values of NSE, PEV and PEPF during calibration range from 0.434 to 0.604, 2.879 to 34.326%, −4.831 to 57.48%, and during validation they are 0.094 to 0.624, −19.52% to −12.55%, and 40.213% to 50.15%. Overall, the performance of SCS-CN model is found more satisfactory than that of SMA model. [ABSTRACT FROM AUTHOR]

CaTiO3 microwave dielectric ceramic was fabricated utilizing traditional two-step sintering process. XRD pattern analysis after Rietveld refinement indicated a pure phase CaTiO3 sample. SEM image illustrated well-crystallized sample with uniform grain sizes and clear grain boundaries. The lattice vibrational characteristics were analyzed by Raman and IR spectroscopy, and the intrinsic properties were calculated in conjunction with the semi-quantum four-parameter (FPSQ) model, which turned out that the low-frequency vibrational modes contribute the most to the dielectric properties. Besides, the real and imaginary parts of the dielectric function were drawn from the FPSQ model. The intrinsic property results fitted from the FPSQ model agree well with the measured values. [ABSTRACT FROM AUTHOR]

Threshold level method is well-known for drought identification with the advantage of its simplicity. However, there is no criterion for classification of drought classes in this method. Therefore, a K index based on threshold level method was proposed and verified to perform well in drought assessment in the Luanhe River basin, China. Meteorological data and remote sensing data were used to calculate the net primary productivity (NPP) of the basin by the CASA model. Results showed that the model had a good performance in comparison with the downloaded yearly remote sensing NPP and monthly PsnNet. The NPP in the basin tended to increase slowly during the year of 2000–2010, and the NPP in the downstream was generally larger than upstream. In three selected representative drought years, drought reduced NPP by about 15–25%, and during the growth season, drought may reduce NPP by about 4.6%, 2.7%, and 1.9% in July, August, and September, respectively, due to reduced precipitation. NPP on grasslands and agricultural land were more susceptible to drought than forests. The result of gray incidence analysis showed that the effects of drought on NPP had a certain delay with about 5 months. [ABSTRACT FROM AUTHOR]

The characteristics of urban pluvial flooding are altering all over the world due to environmental change. In this paper, generalized additive models for location, scale and shape (GAMLSS) was employed to analyze nonstationary frequency of extreme precipitation at subdaily scale. Nonstationary precipitation return periods were estimated using the expected waiting time (EWT) interpretation. A model coupling SWMM and MIKE21 was established, and calibrated and verified by three historical urban floods. Then, it was utilized to simulate urban floods under stationary and nonstationary rainfall conditions with different return periods. The simulated results illustrated that rainfall depth under nonstationarity was greater than that of stationarity when return period was less than 10 years, but the results reversed when the return period was over 20 years. The main variation of rainfall depth occurred within 6 h. The deviation of the maximum water depth was less than 10% for five return levels, and the difference in the longest inundation lengths was 1.2 h for 50-year return period under two assumptions. It may indicate that slight differences of urban flooding were detected between stationary and nonstationary conditions in the study region, which suggested a further study about urban flood under nonstationarity. [ABSTRACT FROM AUTHOR]

Drought propagation is very significant for short-term drought forecast and water resources management. However, the law of drought propagation is still unclear, especially with human activities. In this study, we calibrated and validated the SWAT model in the Luanhe River basin controlled by the Luanxian hydrological station, where there are three large reservoirs upstream and water diversion to Tianjin city. The variable threshold level (VTL) method was employed to identify meteorological and hydrological events both under natural and reservoir-influenced conditions. Drought occurred more frequently, drought duration became longer, and drought deficit became larger with the influence of reservoir regulation and water diversion to Tianjin city. The lag time of hydrological drought onset was shorter and termination longer, i.e., the drought period was more persistent. Multiple regression was used to establish the relations between hydrological drought and the driving factors both under natural and reservoir-influenced conditions. The coefficient of determination is high enough to explain drought propagation. The driving factors were different under the two conditions. The results could provide valuable information for water resource managers. [ABSTRACT FROM AUTHOR]

Flood scaling issue is usually studied under stationary conditions. However, in recent decades, climate change and anthropogenic activities have changed hydrological processes, and stationary assumption has been questioned. To test the flood scaling invariance (simple scaling or multiscaling) and analyze the influence of environmental change on flood scaling parameter, in this study, eight mesoscale sub-watersheds in Daqinghe River basin were selected as the study area, and the trend and change point of annual maximum flood peak (AMFP) series were detected, respectively. All the AMFP series had downward trend, and the change point was around 1979. Therefore, the AMFP series are nonstationary. To analyze the flood scaling issue in the Daqinghe River basin, the AMFP series were reconstructed under the environmental conditions before and after the change point, respectively. Then, flood quantiles were calculated using the reconstructed stationary series. We also used GAMLSS (Generalized Additive Model in Location, Scale and Shape) to calculate flood quantiles based on the observed nonstationary AMFP series. According to the flood quantiles calculated by the above methods, the relationship of the drainage areas of the sub-watersheds and the flood quantiles was fitted with power function. Flood quantiles of the reconstructed stationary and observed nonstationary series showed obvious flood multiscaling. The increase in rainfall depth causes the increase in flood scaling exponents with the increase in return period, and different change ratios of land use before and after change point resulted in the flood scaling exponents of reconstructed series before 1979 were smaller than those after the change point at same return period. [ABSTRACT FROM AUTHOR]

This study investigates the impacts of drought on water supply risk of Panjiakou reservoir in Luanhe River basin of China under environmental change by using a copula-based streamflow series generation approach. To understand how nonstationarity of runoff sequence influences water supply risk, reservoir performance metrics including reliability (time-based and volume-based), resilience, vulnerability, drought risk index (DRI), and sustainability index (SUI) are evaluated with 1956–1979 and 1980–2016 inflows of Panjiakou reservoir, respectively. The results indicated that the prolonged and severe drought may seriously affect the safety of water supply. From two results of generated streamflow time series, the reliability reduction rate reached 58.3% (0.773 to 0.322) when water supply assurance rate was 75% and ecological water level was minimum. Perturbing the copula parameter will make it possible to increase the drought durations and deficits for Panjiakou reservoir to analyze drought impacts on water supply. Based on the reservoir performance metrics, the analysis for Panjiakou reservoir showed that the trend of drought in the future made water supply reliability (time-based and volume-based), resilience, and SUI decrease, but vulnerability and DRI increase, which means the water supply system security became more vulnerable in the future. These results make it easy for decision makers to understand how drought influences future planning and management of Panjiakou reservoir. [ABSTRACT FROM AUTHOR]

The non-stoichiometric Nd[Mg1/2(1+x)Sn1/2]O3 (NMS, − 0.04 ≤ x ≤ 0.04) were synthesized through a routine solid-state reaction process. The phase composition, phonon characteristics, and microwave dielectric properties were investigated by X-ray diffraction patterns, Scanning electron microscopy Raman and Fourier transform far-infrared reflection. The best crystallinity with uniformly distributed grains and clear grain boundaries at x = 0.01. The intrinsic properties were calculated by four-parameter semi-quantum model based on far-infrared reflectivity data, which agree well with those values obtained from the microscopic polarizabilities & damping coefficient angle. The correlations between intrinsic properties and lattice vibrational modes were discussed in particular. [ABSTRACT FROM AUTHOR]

Flood frequency analysis for practical application is traditionally based on the assumption of stationarity, but this assumption has been open to doubt in recent years. A number of studies have focused on the nonstationary flood frequency analysis, and the associated causes of nonstationarity. In this study, the annual maximum flood peak and flood volume of Wangkuai reservoir watershed were used, and several univariate and bivariate models were established to investigate the nonstationary flood frequency, with the distribution parameters changing over the climate indices (NPO, Niño3) and the check dam indices (CDIp, CDIv). In the univariate models, the Weibull distribution performed best and exhibited an undulate behavior for both flood peak and volume, which tended to describe the nonstationarity reasonably well. The bivariate models were constructed using copulas, of which the optimal Weibull distribution in the univariate flood frequency analysis was considered as marginal distributions within the joint distribution. The results showed that the Gumbel-Hougaard copula offered the best joint distribution, and most of the probability isolines crossed each other, which demonstrated the possibility that the occurrence of combinations of the flood peak and volume may be the same under multiple effects of phase changes in the climate patterns and certain human activities (i.e. soil and water conservation). The most likely events were elaborated in diagrams, and the associated combinations of the flood peak and volume were smaller than that estimated by the fixed parameters (i.e. stationary condition) during most of the study period, while it was the opposite in 1956, 1959 and 1963. The results highlight the necessity of nonstationary flood frequency analysis under various conditions in both univariate and multivariate domains. [ABSTRACT FROM AUTHOR]

The spatial and temporal characteristics of drought are investigated for Luanhe River basin, using monthly precipitation data from 26 stations covering the common period of 1958–2011. The spatial pattern of drought was assessed by applying principal component analysis (PCA) to the Standardized Precipitation Index (SPI) computed on 3- and 12-month time scales. In addition, annual SPI and seasonal SPIs (including spring SPI, summer SPI, autumn SPI, and winter SPI) were also defined and considered in this study to characterize seasonal and annual drought conditions, respectively. For all seven SPI cases, three distinctive sub-regions with different temporal evolutions of droughts are well identified, respectively, representing the southeast, middle, and northwest of the Luanhe River basin. The Mann-Kendall (MK) trend test with a trend-free pre-whitening (TFPW) procedure and Sen’s method were used to determine the temporal trends in the annual and seasonal SPI time series. The continuous wavelet transform (CWT) was employed for further detecting the periodical features of drought condition in each sub-region. Results of MK and Sen’s tests show a general tendency of intensification in summer drought over the entire basin, while a significant mitigating trend in spring drought. On the whole, an aggravating trend of inter-annual drought is discovered across the basin. Based on the CWT, the drought variability in the basin is generally dominated by 16- to 64-month cycles, and the 2- to 6-year cycles appear to be obvious when concerned with annual and seasonal droughts. Furthermore, a cross wavelet analysis was performed to examine the possible links between the drought conditions and large-scale climate patterns. The teleconnections of ENSO, NAO, PDO, and AMO show significant influences on the regional droughts principally concentrated in the 16- to 64-month period, maybe responsible for the physical causes of the cyclical behavior of drought occurrences. PDO and AMO also highlight a noteworthy correlation with drought variability on a decadal scale (around 128-month period). The findings of this study will provide valuable references for regional drought mitigation and water resource management. [ABSTRACT FROM AUTHOR]

Drought is regarded as one of the most severe natural disasters globally. This is especially the case in Tianjin City, Northern China, where drought can affect economic development and people's livelihoods. Drought forecasting, the basis of drought management, is an important mitigation strategy. In this paper, we evolve a probabilistic forecasting model, which forecasts transition probabilities from a current Standardized Precipitation Index (SPI) value to a future SPI class, based on conditional distribution of multivariate normal distribution to involve two large-scale climatic indices at the same time, and apply the forecasting model to 26 rain gauges in the Luanhe River basin in North China. The establishment of the model and the derivation of the SPI are based on the hypothesis of aggregated monthly precipitation that is normally distributed. Pearson correlation and Shapiro-Wilk normality tests are used to select appropriate SPI time scale and large-scale climatic indices. Findings indicated that longer-term aggregated monthly precipitation, in general, was more likely to be considered normally distributed and forecasting models should be applied to each gauge, respectively, rather than to the whole basin. Taking Liying Gauge as an example, we illustrate the impact of the SPI time scale and lead time on transition probabilities. Then, the controlled climatic indices of every gauge are selected by Pearson correlation test and the multivariate normality of SPI, corresponding climatic indices for current month and SPI 1, 2, and 3 months later are demonstrated using Shapiro-Wilk normality test. Subsequently, we illustrate the impact of large-scale oceanic-atmospheric circulation patterns on transition probabilities. Finally, we use a score method to evaluate and compare the performance of the three forecasting models and compare them with two traditional models which forecast transition probabilities from a current to a future SPI class. The results show that the three proposed models outperform the two traditional models and involving large-scale climatic indices can improve the forecasting accuracy. [ABSTRACT FROM AUTHOR]

Sm(MgSn)O(SMS) microwave dielectric ceramic was prepared by the traditional solid state synthesis method. The samples were tested by X-ray diffraction (XRD), vibrational spectra (Raman scattering and far-infrared reflectance spectroscopy). The Sm(MgSn)O perovskite is monoclinic with the space group P2/n proved by XRD. Raman vibrational modes were fitted and assigned by Lorentz function. To calculate the intrinsic properties, far-infrared spectra with seven active modes were fitted using a four-parameter semi-quantitative (FPSQ) model. The dielectric constant calculated according to FPSQ is similar to that obtained from the molecular polarization and the Clausius equation. The intrinsic loss has been determined by the relationship between the damping factor and the spectral center frequency, which is slightly larger than the value obtained in the four-parameter fitting, and indicates that A(Sm) Raman mode has a enormous effect on the dielectric loss. F and F have the greatest contribution to the dielectric constant and loss. Finally, the real and imaginary parts of permittivity were analyzed with Kramers-Krönig transformation. [ABSTRACT FROM AUTHOR]

The frequency of drought occurring in the Luanhe River basin in China has increased since 1965. The severe droughts are mainly influenced by the negative phase of Arctic Oscillation (AO) and the 12-month time-lag La Niña events. In this study, we investigate the mechanism of the severe droughts occurring in the Luanhe River basin due to the 12-month time-lag Pacific sea-surface temperature anomaly (SSTA) and AO in the Luanhe River basin for the period of 1965-2012. According to the 3-month time scale of the low-level circulations and SSTA in the Pacific Ocean, when AO is in a continuous negative phase, the geopotential height at the 500-hPa level over high-latitude regions, such as Siberia, Lake Baikal and the Ural Mountains, decreases. The Europe-Asia wave train is located southward, which results in meridional anomalous circulation prevailing over East Asia. Due to air-sea interactions, the 12-month time-lag Pacific SSTA weakens the northwestern Pacific subtropical high and blocks the warm air from the Pacific. When the negative phase of AO and La Niña happened simultaneously during 1971/1972, the first stage of 2000/2002 and 2008/2009, a severe drought occurred in the Luanhe River basin. A severe drought happened in this region during 1980/1981 and the third stage of 2000/2002 when AO was in the negative phase. [ABSTRACT FROM AUTHOR]

Several small reservoirs and a large number of check dams had been constructed in the Wangkuai reservoir watershed after 1970s, and flood time series lacked stationarity, which affected the original design flood hydrographs for the Wangkuai reservoir. Since the location, storage capacity and drainage area of the large number of check dams were unknown, we present a method to estimate their total storage capacities (TSC) and total drainage areas (TDA) by using the recorded rainstorm and flood data. On the basis of TSC and TDA, the flood events which occurred in an undisturbed period were reconstructed under current conditions to obtain a stationary flood series. A frequency analysis was subsequently performed to assess the design flood peak and volume for both small and medium design floods with a 10-200 year return period. For large and catastrophic floods, it was assumed that the upstream check dams and small reservoirs would be destroyed, and water stored in these hydraulic structures were re-routed to the Wangkuai reservoir by unit hydrograph. The modified flood peak and volume decreased for floods with a 10-200 year return period when compared to the current design flood. But for large design floods with a return period exceeding 500 years, peak discharge increased. This study provides a new method for design flood calculation or modification of the original design flood in watersheds with a large number of check dams. [ABSTRACT FROM AUTHOR]

Drought and water scarcity often occur simultaneously and are confused by water resources managers, because it is not easy to distinguish the two phenomena. In this study, we selected Luanhe river basin as the study area in which land use changed and a number of check dams were constructed. According to the situation in this river basin, we proposed the concepts of watershed drought (WD), watershed water scarcity (WWS) and streamflow water scarcity (SWS) based on the previous studies and made comparisons of the three concepts by a conceptual figure. A hydrological model was essential to separate the three concepts. Therefore, the Soil and Water Assessment Tool was calibrated and validated using hydrometeorological data and land surface data in undisturbed period in four sub-watersheds. Then the discharges in disturbed period were simulated under undisturbed and disturbed land use conditions without check dams, respectively. Compared with the variable threshold values, the features of WD, WWS and SWS were quantified. It was found that the mean duration of WD was the longest among the three phenomena and the maximum duration of WD could last more than 4 years. Water deficit caused by WD was the largest among the three phenomena, too, and it was about twice greater than water deficit caused by SWS in the four selected sub-watersheds. The method in this study is significant to separated drought and water scarcity in similar watersheds, and the results could provide significant information for water resources managers to make decision to predict drought and combat water scarcity. [ABSTRACT FROM AUTHOR]

Runoff variations were influenced by climate variability and land surface change, but the mechanism was not clear, and quantification of their effects was not mature. To find a reliable method, we selected four sub-watersheds in Luanhe watershed in which runoff series had significant downward trends. We first calibrated and validated the Soil and Water Assessment Tool (SWAT) hydrological model by using the hydrometeorological data in reference period in the four sub-watersheds. The simulated runoff series agreed well with the observed ones, which demonstrated the model performed well. Then we reconstructed the runoff series in impaired period under 1970 and 2000 land use conditions without check dams. According to the simulation results, the contributions of precipitation variability, land use change and construction of large number of check dams were quantified by traditional method. It was found that precipitation variability was the main cause of runoff decrease. In this study, we proposed a new perception for distinguishing the contributions of land surface change and precipitation variability, and got different results from traditional method. Precipitation variability was the main factor for runoff decrease in Luanhe and Wuliehe sub-watersheds, and land surface change contributed more in Yixunhe and Liuhe sub-watersheds. The combined effects were not the summation of single effect of precipitation variability and land surface change. It is of great necessity to do further research on this issue, and will provide reliable information for water resources managers. [ABSTRACT FROM AUTHOR]

Loglinear models for three-dimensional contingency tables was used with data from 21 rainfall stations and 7 hydrometric stations in the Luanhe river basin, northeast China, for short term prediction of drought severity class. Loglinear models were fitted to drought class transitions derived from standardized precipitation index (SPI) and standardized runoff index (SRI) time series to find which series was more suitable for hydrological drought class prediction 1 and 2 months ahead, respectively. Expected frequencies for two consecutive transitions between drought classes were first calculated, and based on this the predicted drought classes 1 and 2 months ahead were obtained. The results showed that despite the contingency tables of drought class transitions presented the maintenance of the precedent drought class, results of three-dimensional loglinear modeling presented good results when comparing predicted and observed drought classes. Only for a few cases predictions did not fully match the observed drought class, mainly for 2-month lead and when the SRI values are near the limit of the severity class predicted by SRI time series. Based on the correlation analysis of SPI and SRI, we presented the well-known method of hydrological drought class prediction by SPI time series. It was found that, using loglinear regression method, the accuracy of predictions for 2-month lead predicted by SPI time series was higher than those predicted by SRI time series. When we divided the SPI and SRI time series into 2 sub-periods (pre- and post-1980 where land cover changed), we got the same drought class prediction as that predicted by the entire SPI and SRI time series, which illustrated that changes in land use did not affect predictions of hydrological drought classes in the Luanhe river basin. It could be concluded that loglinear prediction of drought class transitions is a useful tool for short term hydrological drought warning, and the results could provide significant information for water resources managers and policy makers to mitigate drought effects. [ABSTRACT FROM AUTHOR]

Traditionally, flood frequency analysis under the assumption of stationarity has been a cornerstone and there is mature technology applied in practice. However, recent evidences of the impact of climate variability and anthropogenic factors have thrown into question the applicability of stationary hypothesis. In this study, Kendall's tau and Spearman's rho correlation test were adopted to detect the relationship between climate indices (PDO, NAO, AO, NPO and ENSO) and annual flood peak data. The test results showed that NPO and Niño3 had significant correlations with the flood peak which could prove the climate cause of non-stationarity. Niño3 is used herein to describe ENSO. We also proposed a check dam index (CDI) to represent the effect of human activities that caused nonstationarity on flood. The CDI was based on the estimated storage capacity and drainage area of large number of check dams and small hydraulic structures. A framework for nonstationary flood frequency analysis was developed through Generalized Additive Models in Location, Scale and Shape (GAMLSS), and two models based on GAMLSS were applied to the annual flood peak. The model results that incorporated climate indices (NPO and Niño3) and CDI as covariates in the parameters of the selected distribution exhibited an undulate behavior, which could better describe nonstationarity than the model with only time dependence. For a reservoir index (RI) proposed by López and Francés () which is similar to CDI, we established two contrast models and the result revealed that CDI is superior to RI. These results highlight the necessity of flood frequency analysis under nonstationary conditions, and alternative definitions of return period should be adapted. [ABSTRACT FROM AUTHOR]

In a rapidly changing environment, a greater concern about the establishment and improvement of drought indices is expected. The main goal of this study is to develop and apply a time-dependent Standardized Precipitation Index (SPIt) that takes account of the possible non-stationary behaviors in precipitation records. Summer precipitation observations (1959 ~ 2011) from 21 raingauge stations in the Luanhe River basin are fitted with non-stationary Gamma distributions respectively by means of the Generalized Additive Models in Location, Scale and Shape (GAMLSS). The temporal variability of the distribution's parameter (related to the mean) is flexibly described by an optimized polynomial function. Based on the non-stationary distribution, the SPIt is calculated and then employed to assess the spatio-temporal characteristics of summer drought in the basin. Results of the non-stationary modeling indicate an overall decreasing trend in the summer precipitation during 1959 ~ 2011, and especially a significant decrease in the period of 2000 to 2011. The SPIt is found to be more robust and reliable compared with the traditional Standardized Precipitation Index (SPI). Moreover, remarkable difference is observed between the historical drought assessments of SPIt and SPI in the Luanhe River basin, implying that the non-stationarity of hydrological time series cannot be ignored in drought analyses and forecasts. The proposed SPIt method can be a feasible alternative for drought monitoring under non-stationary conditions, intended to provide a valuable reference for further studies. [ABSTRACT FROM AUTHOR]

Evaluation of the impact of climate variability and human activities on hydrological drought is of great significance for drought mitigation strategies. In this study, standardized runoff index (SRI) at various time scales is used to characterize hydrological droughts in the Luanhe River basin, northeast of China, for the period of 1959-2011. Correlation analysis is conducted to examine the associations between the hydrological droughts and large-scale oceanic-atmospheric patterns (AMO and ENSO). Climate-induced and human-induced influence indices are also developed based on standardized precipitation index and SRI to investigate the possible influences of the climate patterns and human activities on the hydrological droughts. Results indicate that the significant influence of AMO on hydrological drought at different time scales is evident among different months across the Luanhe River basin, with warm (cold) AMO phases favoring drought (wet) conditions. The direct linkage of ENSO to hydrological drought is relatively weak in the basin, while the extent of the linkage can be improved with increasing time lags. Moreover, El Niño phases show a closer relation with the drought events of the region as compared with La Niña phases. It is also implied that human activities exhibit aggravating effects on hydrological drought at shorter time scales over the basin, whereas they might show mitigating effects at longer time scales in some areas of the basin. These findings can be beneficial for better understanding how the hydrological drought responses to climate changes and human activities, thereby providing valuable references for drought forecasts and water resources managements in the Luanhe River basin. [ABSTRACT FROM AUTHOR]

Recent evidences of the impact of regional climate variability, coupled with the intensification of human activities, have led hydrologists to study flood regime without applying the hypothesis of stationarity. In this study, identification of nonstationarity was conducted in the form of both trend and change point in the mean of the annual maximum flood magnitudes, using Mann-Kendall and Pettitt test, respectively in Wangkuai reservoir watershed, China. The annual maximum flood series exhibited a significant decreasing trend, and the timing of change point was detected in 1979, which was consistent with the construction of large numbers of check dams and small hydraulic structures. A correlation test (Pearson correlation test) between large-scale oceanic-atmospheric patterns (El Niño Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), North Pacific Oscillation (NPO), North Atlantic Oscillation (NAO), Atlantic Oscillation (AO)) and annual maximum flood peaks was adopted to assess the climatic causes of nonstationary flood series. It was found that NPO, NAO and AO had significant correlations with flood peak, but ENSO and PDO could not explain the variations of flood peak. In the case of human-induced nonstationarity, we proposed 2 new indices to represent the effect of human activities on flood. The new indices were proposed based on the storage capacity and drainage area of the large numbers of check dams and small hydraulic structures which were estimated with no observed data. The identification of nonstationarity for flood series and the climatic and human-induced causes could provide useful information in nonstationary flood frequency analysis. [ABSTRACT FROM AUTHOR]

Annual runoff in Luanhe river basin was detected a downward trend and caused water crisis in Tianjin, China. To quantify the decreased runoff volume, Mann-Kendall test and Pettitt test were employed to check whether there existed significant trend and change points for annual rainfall and runoff time series in Panjiakou reservoir basin and 8 sub-watersheds. It was found that the annual runoff time series had a significant downward trend at 5 % confidence level, and the change point was at 1979 in Panjiakou reservoir watershed. Then double mass curve of annual rainfall and annual runoff was plotted, and two lines were fitted before and after 1979, respectively. Based on this method, the comprehensive effects of land use/land cover change on annual runoff were estimated. To further quantify the contributions of each main factor to annual runoff decrease, water stored in check dams and social water use in different periods were surveyed first. And then multi-linear regression was used to develop the relations between annual runoff and the driven factors. Water area decrease was identified to be the main factor contributing to annual runoff reduction. The results in this study can provide valuable information for water resources planners and policy makers. [ABSTRACT FROM AUTHOR]

Change point detection is an effective tool to identity whether the hydrological data are of consistency. In this paper, Pettitt test was first used to detect change point for annual rainfall and runoff time series in 6 selected sub-watersheds of Luanhe river basin in Northeast part of China. Then we presented a method to detect change point according to the law of mutual change of quality and quantity in variable fuzzy sets. We chose the mean of time series as assessment index as in other change point detection methods, and defined 95 and 5 % quantiles of the time series as the supremum and infimum respectively. We selected a reference period (for example, the first 10 points of the time series) as the stationary period, and after the reference period, we checked the mean value of the time series point by point. We used this method in the 6 sub-watersheds of Luanhe river basin. The results of the 2 methods showed that most annual rainfall time series had no change point, and some annual runoff time series had change point in 1979 or 1981. Comparison of the 2 methods was made, and it indicated that Pettitt test provided reference for variable fuzzy sets method, but the latter provided more reasonable results than Pettitt test in this study. This method can also be used in other natural time series. [ABSTRACT FROM AUTHOR]

Land use has changed in the Daqinghe watershed during 1956-2005, and it has influenced the flood peak and volume. In order to reveal the effects of land use change on flood characteristics in Daqinghe watershed, we selected 2 sub-watersheds and used remote-sensed land use data of 1980 and 1996 to analyze changes in land use and also selected several combinations of similar rainfall events and the corresponding flood events to show how changes in land use affect floods. The forest and urban area increased and other types decreased, and flood peaks and volumes tended to decrease under similar rainfall events. To quantify the extent of change in land use affecting floods, a hydrological model incorporating the land use was established. The model combines infiltration excess and saturation excess runoff generation mechanism in each type of land use, and the simulation results agreed well with the measured flood processes in the two selected watersheds. Several floods of different return intervals were selected to be modeled under the 1980 and 1996 land use conditions. The results show that both flood peak and volume decreased under the 1996 land use condition in comparison with the 1980 land use condition in the two watersheds. Most of the flood peaks decreased <5 %, but the volume decreased to a greater extent. This result can be helpful in modifying design flood. [ABSTRACT FROM AUTHOR]

Affected by human activities, land use and land cover has changed in Daqinghe watershed, China, which resulted in varied runoff. In many hydrological stations, there was a decreasing trend of flood volume and flood peak, but no trend of rainfall depth. In order to quantify the effect of land use change on flood peak and volume, we selected 5 sub-watersheds in Daqinghe watershed, and made a multi-linear regression analysis incorporating the main information in the selected sub-watersheds. The dependent variables are changes in flood volume and flood peak, and the independent variables are the control factors including changes in rainfall depth, intensity, land use area, watershed area, and so on. The rainfall and flood data series are from 1956 to 2005. We divided the data into 2 groups according to flood size―greater than and less than 10 year return period. At last, 4 regression equations were obtained. Based on the multi-linear regression equations and land use data of 1970, 1980, 1995 and 2000, the quantified effects of land use change on flood peak and volume were obtained. Compared with 2000 land use condition, flood volume and peak varied larger in 1970 and 1995 land use conditions, but slightly in 1980 land use condition. Take Zijingguan as an example, flood volume greater than 10 year return period increased 4.08 mm in 1970 land use and decreased 4.90 mm in 1995 land use, but just increased 0.12 mm in 1980 land use. Among all the selected sub-watersheds, land use change had a significant effect on both flood volume and peak in Zijingguan and Zhangfang sub-watersheds. And Manshuihe showed a large variation in 1970 land use condition, other sub-watersheds exhibit a moderate variation due to land use change. [ABSTRACT FROM AUTHOR]

The techniques of homology cloning and anchored PCR were used to clone the peroxiredoxin (Prx) gene from black tiger shrimp ( Penaeus monodon). The full length cDNA of black tiger shrimp Prx (PmPrx) contained a 5′ untranslated region (UTR) of 51 bp, an ORF (open reading frame) of 582 bp encoding a polypeptide of 193 amino acids with an estimated molecular mass of 22.15 kDa and a 3′ UTR of 948 bp. Sequence comparison showed that PmPrx shared higher identities with Prx IVs than that with other isoforms of Prx, indicating PmPrx was a member of the Prx IV family. A quantitative reverse transcriptase Real-Time PCR (qRT-PCR) assay was developed to assess the mRNA expression of PmPrx in different tissues and the temporal expression of PmPrx in the hepatopancreas challenged by lipopolyssacharide (LPS). Higher-level mRNA expression of PmPrx was detected in the tissues of hepatopancreas, gonad and heart. The expression of PmPrx in the hepatopancreas was up regulated after stimulated by LPS. The results indicated that PmPrx was a constitutive and inducible expressed protein and could be induced by LPS. [ABSTRACT FROM AUTHOR]

The decrease of runoff in the Luanhe river basin, which caused water crisis in Tianjin for several times, was investigated using discharge data covering the period 1956–2002. The data from the differential integral curves of the annual runoff indicate that the decreasing point began in 1979 in the six sub-basins. The decrease of runoff in the Luanhe river basin resulted from the combination of climate effects and human activities, in which the latter plays an important role. This can be illustrated by noting that after 1979 the runoff generated by similar precipitation decreased under the condition that the total precipitation did not decrease in the entire basin. As a result, the annual runoff of the Luanhe river basin after 1979 decreased by about 6.46 × 108 m3 each year. To analyze the runoff characteristics, it is inadequate to seek the runoff trends only and the identification of cyclical component of the runoff as accurate as possible is necessary. From the natural annual runoff discharge time series, we can see the annual runoff fluctuates around the long-term average. Analyzed by VRL (Variable Record Length) method, the main periods of 3, 5–6, 7, 9, 16–20 and 37–39 years were found. The last decade causing water crisis was the driest period in the history, and this condition will last several years from trend analysis and power spectrum analysis. So finding new water sources is urgent to solve water crisis in Tianjin city, and the South-North Water Transfer is a feasible option. [ABSTRACT FROM AUTHOR]