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Accounting for over 70% of global water withdrawals, irrigation plays a crucial role in the development of agriculture. Irrigation water requirement ( WIRR ) will be influenced by climate change due to the alteration in soil water balances, evapotranspiration, physiology and phenology under global warming. This is particularly true for rice, a high water-consuming crop. Therefore, exploring the impact of climate change on rice WIRR is of great significance for the sustainable utilization of water resources and food security. This paper aims to investigate spatially and temporally the responses of rice WIRR to climate change in the middle and lower reaches of the Yangtze River (MLRYR), which is one of the most important rice farming districts in China. With the help of the specially developed rice growing period calculation method and water balance model coupled with rice irrigation scheduling, the impacts of climate change on WIRR for early rice, late rice and single cropping rice during the historical (1961–2012) and future (2011–2100) periods were evaluated. Meanwhile, to consider the uncertainty from climate models in future projection, four GCMs under RCP2.6, RCP4.5 and RCP8.5 emission scenarios from the 5th Coupled Model Intercomparison Project (CMIP5) were employed as the input of the water balance model. The results indicate the following: (1) The days of growing period ( DGP ) for all three types of rice display shortened trends in historical and most future periods. However, in the middle region of the MLRYR, the DGP for early rice and late rice would increase by up to10 days in 2080s under RCP8.5 scenario. (2) Over the past 50 years, the WIRR significantly decreased by 1.58 and 2.10 mm yr −1 for late rice and single cropping rice, respectively. While for early rice, the WIRR only slightly decreased by 0.13 mm yr −1 . (3) Projected future WIRR would increase for all three types of rice in the whole region under RCP4.5 and RCP8.5 scenarios (up to 100 mm), but decrease for single cropping and late rice in the southeast region (up to 40 mm). The results can provide beneficial reference and comprehensive information to understand the impact of climate change on the agricultural water balance and improve the regional strategy for water resource utilization and agricultural management in the middle and lower reaches of the Yangtze River. [ABSTRACT FROM AUTHOR]

Substantial climate change and intensive anthropogenic activities hamper efforts to explain and predict the variability of the terrestrial water balance. The Budyko framework has recently seen a renaissance in hydrological research due to the framework’s comprehensiveness and effectiveness for studying the effects of global change on water resources. In this paper, the development of the Budyko framework is analysed first. The temporal and spatial variability for the Budyko hypothesis are subsequently elaborated. On finer temporal scales, more processes need to be considered, and the degree of control exerted by individual factors on the water balance varies with the spatial scale considered. Finally, perspectives regarding better understanding and application of the Budyko framework at the catchment scale are provided. A representative and diverse catchment data set is required to estimate the parameter in the model. The co-evolution of landscape characteristics and climate properties would be beneficial to improve the Budyko framework with respect to model parsimony and the physical background. It is necessary to illuminate how the empirical Budyko curve would change under climate change. The general laws for selecting variables and statistical methods for improving Budyko models still need to be explored. [ABSTRACT FROM AUTHOR]

Water resources are influenced by various factors such as weather, topography, geology, and environment. Therefore, there are many difficulties in evaluating and analyzing water resources for the future under climate change. In this paper, we consider climate, land cover and water demand as the most critical factors affecting change in future water resources. We subsequently introduce the procedures and methods employed to quantitatively evaluate the influence of each factor on the change in future water resources. In order to consider the change in land cover, we apply the Multi-Regression approach from the cellular automata-Markov Chain technique using two independent variables, temperature and rainfall. In order to estimate the variation of the future runoff due to climate change, the data of the SRES A2 climate change scenario were entered in the SLURP model to simulate a total of 70 years, 2021-2090, of future runoff in the Han River basin in Korea. However, since a significant amount of uncertainties are involved in predicting the future runoff due to climate change, 50 sets of daily precipitation data from the climate change scenario were generated and used for the SLURP model to forecast 50 sets of future daily runoff. This process was used to minimize the uncertainty that may occur when the prediction process is performed. For future water balance analysis, the future water demand was divided into low demand, medium demand and high demand categories. The three water demand scenarios and the 50 daily runoff scenarios were combined to form 150 sets of input data. The monthly water balance within the Han River basin was then calculated using this data and the Korean version of Water Evaluation and Planning System model. As a result, the future volume of water scarcity of the Han River basin was predicted to increase in the long term. It is mostly due to the monthly shift in the runoff characteristic, rather than the change in runoff volume resulting from climate change. [ABSTRACT FROM AUTHOR]

This paper demonstrates the impracticality of a comprehensive mathematical definition of the term 'drought' which formalises the general qualitative definition that drought is 'a deficit of water relative to normal conditions'. Starting from the local water balance, it is shown that a universal description of drought requires reference to water supply, demand and management. The influence of human intervention through water management is shown to be intrinsic to the definition of drought in the universal sense and can only be eliminated in the case of purely meteorological drought. The state of drought is shown to be predicated on the existence of climatological norms for a multitude of process-specific terms. In general, these norms are either difficult to obtain or even non-existent in the non-stationary context of climate change. Such climatological considerations, in conjunction with the difficulty of quantifying human influence, lead to the conclusion that we cannot reasonably expect the existence of any workable generalised objective definition of drought. [ABSTRACT FROM AUTHOR]

This paper examines the actions toward the reduction of greenhouse gas emissions to the atmosphere that Greece has implemented to comply with international conventions and the Kyoto Protocol. It also concerns the analysis and processing of climate variables and the assessment of the impact of climate change on water resources in Northern Greece and on some critical water management issues, such as reservoir storage and water supply for agriculture and domestic use. Initially, a monthly conceptual water balance model was applied to estimate runoff values in the entrance of the Polyfyto reservoir under the UKHI equilibrium scenario referring to the year 2100. It was found that the mean annual runoff, mean winter runoff and summer runoff values will be reduced. Increases of the risks associated with the annual quantities of water supply have been observed. [ABSTRACT FROM PUBLISHER]

Summary: The paper describes a set of modelling utilities (a root-zone model, a grid-distribution tool, and a modified Modflow-2000 model) that can be used to simulate the water cycle of a city in terms of root-zone water balance, water supply, wastewater, storm runoff, groundwater flow, streamflow, and the interactions between these subsystems. The utilities are used to simulate the water cycle in the Copenhagen area (976km2) during the period 1850–2003. Long-term time series of hydraulic head, streamflow, and inflow to sewage works have been used to manually calibrate the model parameters. We used a step-wise calibration strategy, using different parts of the data in the various steps, to calibrate hydrogeological parameters, storm runoff parameters, and parameters governing the interactions between groundwater and leaky pipe systems, respectively. Simulations indicate that present rates of groundwater leakage into streams, lakes, and wetlands constitute 60% of pre-urbanization levels due to massive groundwater extraction. However, the current problems of groundwater shortages and streamflow depletion would have been far worse, if precipitation had not increased by 20% since 1850. Model simulations indicate that urbanization has lowered current groundwater recharge due to the establishment of impervious areas and due to negligible contributions from leaky pipe systems. This is opposite to the reported general tendency of enhanced recharge due to urbanization. However, current recharge rates within Copenhagen are simulated to be 20% higher than prior to urbanization, which is attributed to the increase in precipitation during the study period. [ABSTRACT FROM AUTHOR]

The need for efficient water resources management is currently more pressing than ever, considering population growth and increased reliability requirements, under climate change conditions. On average, one-third of the total water abstracted for urban uses is being lost due to leaks and breaks occurring in water distribution networks. This means that significant amounts of water and revenues are being lost, forcing water utilities to consider developing effective water loss and Non-Revenue Water reduction strategies. Additionally, all water utilities operating in EU countries should, by the end of 2010, develop and implement appropriate water pricing policies that will guarantee the recovery of the full cost of the water being used. This strict obligation makes the reduction of water losses an even more urgent goal that the water utilities have to achieve. The first step towards all the above-mentioned goals is to safely evaluate the performance level of the water network. Thus, the IWA Task Forces on Water Losses and Performance Indicators (PIs) developed specific tools (e.g., the standard international water balance and various PIs), to help water utilities use a common language that will assist know-how and experience exchange through an effective benchmarking process. The paper presents the results of using the above-mentioned IWA tools, in the case of the Larisa city water distribution network in Greece. This is the first time that such an attempt has taken place in Greece. During this process, the problems faced and the ways to tackle them are analyzed, focusing on the role of key factors that had to do with local conditions. Larisa's results are compared to data available from similar cases. Sensitivity analysis was used to check the impact of the variables' uncertainty to the results. Finally, water loss reduction measures are proposed towards an effective pressure management strategy and a proactive pipe maintenance policy based on safely estimating the pipes' optimum replacement time. [ABSTRACT FROM AUTHOR]

Abstract: In the North China Plain (NCP), while irrigation using groundwater has maintained a high-level crop productivity of the wheat–maize double cropping systems, it has resulted in rapid depletion of groundwater table. For more efficient and sustainable utilization of the limited water resources, improved understanding of how crop productivity and water balance components respond to climate variations and irrigation is essential. This paper investigates such responses using a modelling approach. The farming systems model APSIM (Agricultural Production Systems Simulator) was first calibrated and validated using 3 years of experimental data. The validated model was then applied to simulate crop yield and field water balance of the wheat–maize rotation in the NCP. Simulated dryland crop yield ranged from 0 to 4.5tha−1 for wheat and 0 to 5.0tha−1 for maize. Increasing irrigation amount led to increased crop yield, but irrigation required to obtain maximum water productivity (WP) was much less than that required to obtain maximum crop yield. To meet crop water demand, a wide range of irrigation water supply would be needed due to the inter-annual climate variations. The range was simulated to be 140–420mm for wheat, and 0–170mm for maize. Such levels of irrigation applications could potentially lead to about 1.5myear−1 decline in groundwater table when other sources of groundwater recharge were not considered. To achieve maximum WP, one, two and three irrigations (i.e., 70, 150 and 200mmseason−1) were recommended for wheat in wet, medium and dry seasons, respectively. For maize, one irrigation and two irrigations (i.e., 60 and 110mmseason−1) were recommended in medium and dry seasons, while no irrigation was needed in wet season. [Copyright &y& Elsevier]

Abstract: In this paper we present a modelling study to investigate the impacts of climate change on the chloride concentration and salinisation processes in two man-made freshwater lakes in the Netherlands, Lake IJsselmeer and Lake Markermeer. We used a transient compartmental chloride and water balance model to elucidate the salinisation processes occurring under present conditions and assess future salinisation under two climate forcing scenarios. The model results showed that the Rhine River is the dominant determinant for the chloride concentration in both lakes, followed by drainage of brackish groundwater from the surrounding polders. The results further show that especially during dry years, seawater intrusion through the tidal closure dam is an important source of chloride to Lake IJsselmeer. The results from the climatic forcing scenarios show that Lake IJsselmeer is especially vulnerable to climate-induced salinisation whereas effects on Lake Markermeer are relatively small. Peak chloride concentrations at the raw water intake of the Andijk drinking water facility on Lake IJsselmeer are projected to increase to values above 250 mg/l in the most far-reaching climate change scenario W+ in 2050 for dry years. This is well above the maximum allowable concentration of 150 mg/l for chloride in drinking water. Modelling showed that climate change impacts the chloride concentrations in a variety of ways: 1) an increasing occurrence of low river flows from summer to autumn reduces the dilution of the chloride that is emitted to the Rhine with a constant load thereby increasing its concentration; 2) increased open water evaporation and reduced rainfall during summer periods and droughts increases the chloride concentration in the water; and 3) rises in sea level increase seawater intrusion through the tidal closure dam of Lake IJsselmeer. The processes described here are likely to affect many other tidal rivers or lakes and should be considered when planning future raw water intake stations for drinking water production or agricultural water supply. [Copyright &y& Elsevier]

The impact of climate change on the hydrological regime and water resources in the basin of Venetikos has been assessed in this paper. Venetikos is a sub-basin of the Aliakmon River Basin, located in northern Greece. A monthly conceptual water balance model was calibrated using historical hydrometeorological data to determine changes in stream-flow runoff under two different equilibrium scenarios (UKHI, CCC) for year 2020, 2050 and 2100. The application of the two scenarios resulted in reduction of the mean winter and summer runoff values, and increase in maximum annual and decrease in minimum annual runoff values. Additionally, an increase of potential and actual evapo-transpiration was noticed due to temperature increase. As a result, a reduction of snow accumulation, as well as a decrease in spring runoff values and soil moisture are expected. A shift of the wet period towards December is remarked, resulting in severe prolongation of the dry period. Consequently, the water policy should be revised in order to address the above possible future changes. [ABSTRACT FROM AUTHOR]

Climate change will induce an increasing drought risk in western and southern Europe and a resulting increase in water stress. This paper investigates the impact of both the extreme hot and dry summer of 2003 and the PRUDENCE CHRM climate change scenario summer for 2071-2100 on the monthly water balance (available water resources versus water demand) within the Kitzbueheler Region in the Austrian Alps. As a baseline period the climate normal period from 1961 to 1990 was chosen. In both summer scenarios total flow and ground water recharge decrease substantially, due to the decrease in precipitation and increase in evapotranspiration However, regional water availability is still sufficient to serve all water demand stakeholders. As a result of decreased snow cover duration, flow seasonality changes within the CHRM scenario. Especially springs are very vulnerable to these climatological conditions; average local groundwater recharge is reduced by 20% up to 70% within both scenarios. Due to the hydrogeological characteristics of the case study area and the typical small structured alpine water supply infrastructure, local deficits can occur. But also groundwater aquifers in the valleys show a decrease in water availability. These results are supported by observations made in 2003 throughout Austria and Switzerland. [ABSTRACT FROM AUTHOR]

• Increased precipitation and temperature are expected under 1.5/2.0 °C warming in Central Asia. • ETc is projected to increase in Central Asia under 1.5 °C and 2.0 °C global warming. • Water gap (precipitation-CWR) will widen for rainfed north Kazakhstan and irrigated Fergana. In the arid region of Central Asia, climate change leads not only to changes in water availability generated by glacier/snow melt in the alpine regions, but also to changes in water consumption. This paper evaluates agricultural water demand and water supply (represented by precipitation) for the five Central Asian countries (Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan) under global warming conditions of 1.5 °C and 2.0 °C. As Central Asia is more sensitive to climate change compared to the global average, the temperature is predicted to rise by 1.7 °C and 2.6 °C and precipitation to increase by 9 % and 12 % in global warming scenarios of 1.5 °C and 2.0 °C, respectively. The average crop water requirement (CWR) is expected to increase by 13 mm and 19 mm per year, respectively, under the global warming scenarios of 1.5 °C and 2.0 °C. A widening gap between water supply and water demand is expected compared to the historical period (1976–2005) under global warming scenario of 2.0 °C. Under global warming of 2.0 °C, the anticipated water gaps between precipitation and CWR are projected to increase by 2.8 × 108 m3 and 1.5 × 108 m3 for the rainfed north Kazakhstan region and the irrigated Fergana region while the increase of precipitation could able to meet the increase in CWR under global warming of 1.5 °C. Investigating the water balance for major planting areas in water-limited Central Asia could provide a scientific basis for sustainable development of the entire region. [ABSTRACT FROM AUTHOR]