Impact of water demand on hydrological regime under climate and LULC change scenarios

The present study focuses on an assessment of the impact of future water demand on the hydrological regime under land use/land cover (LULC) and climate change scenarios. The impact has been quantified in terms of streamflow and groundwater recharge in the Gandherswari River basin, West Bengal, India. dynamic conversion of land use and its effects (Dyna-CLUE) and statistical downscaling model (SDSM) are used for quantifying the future LULC and climate change scenarios, respectively. Physical-based semi-distributed model Soil and Water Assessment Tool (SWAT) is used for estimating future streamflow and spatiotemporally distributed groundwater recharge. Model calibration and validation have been performed using discharge data (1990–2016). The impacts of LULC and climate change on hydrological variables are evaluated with three scenarios (for the years 2030, 2050 and 2080). Temperature Vegetation Dyrness Index (TVDI) and evapotranspiration (ET) are considered for estimation of water-deficit conditions in the river basin. Exceedance probability and recurrence interval representation are considered for uncertainty analysis. The results show increased discharge in case of monsoon season and decreased discharge in case of the non-monsoon season for the years 2030 and 2050. However, a reverse trend is obtained for the year 2080. The overall increase in groundwater recharge is visible for all the years. This analysis provides valuable information for the irrigation water management framework.     

气候变化下长江中下游水稻灌溉需水量时空变化特征

选择长江中下游单季中稻为研究对象,结合45个气象站1961~2010年逐日气象资料,基于统计降尺度模型(SDSM),生成HadCM3气候模式A2和B2两种情景下各站点参考作物腾发量和降水数据。基于联合国粮食及农业组织(FAO)推荐的作物系数法,并考虑有效性降雨和不同地区深层渗漏量,分析历史和未来的水稻灌溉需水时空变化特征。结果表明:过去50年,除了太湖流域以外的长江中下游大部分区域的参考作物腾发量和水稻需水量都呈显著下降趋势,而显著下降的水稻灌溉需水量主要位于鄱阳湖流域;未来两种情景下,参考作物腾发量、水稻需水量和水稻灌溉需水量均值都呈下降趋势,但水稻灌溉需水量降幅最小;水稻需水量和水稻灌溉需水量在长江中下游地区的变化趋势具有明显的空间异质性,水稻需水量大幅减少的区域由太湖流域向汉江和洞庭湖流域扩展。未来水稻灌溉需水量减少的区域主要分布在太湖流域、汉江流域东部和洞庭湖流域北部,并随时间推移呈扩大趋势。     

Comparison of logistic regressions and snowfall intensity–duration threshold as forecasting tools for direct-action snow avalanches in the Presidential Range,New Hampshire,USA

Built environment, which includes some major investments in Oman, has been designed based on historical data and do not incorporate the climate change effects. This study estimates potential variations of the hourly annual maximum rainfall (AMR) in the future in Salalah, Oman. Of the five climate models, two were selected based on their ability to simulate local rainfall characteristics. A two-stage downscaling–disaggregation approach was applied. In the first stage, daily rainfall projections in 2040–2059 and 2080–2099 periods from MRI-CGCM3 and CNRM-CM5 models based on two Representative Concentration Pathways (RCP8.5 and RCP4.5) were downscaled to the local daily scale using a stochastic downscaling software (LARS-WG5.5). In the second stage, the stochastically downscaled daily rainfall time series were disaggregated using K-nearest neighbour technique into hourly series. The AMRs, extracted from 20 years of projections for four scenarios and two future periods were then fitted with the generalized extreme value distribution to obtain the rainfall intensity–frequency relationship. These results were compared with a similar relationship developed for the AMRs in baseline period. The results show that the reduction in number of wet days and increases in total rainfall will collectively intensify the future rainfall regime. A marked difference between future and historical intensity–frequency relationships was found with greater changes estimated for higher return periods. Furthermore, intensification of rainfall regime was projected to be stronger towards the end of the twenty-first century.     

SRA1B情景下中国主要作物需水预测

分析气候变化下中国主要作物需水规律,有助于从粮食安全与水资源可持续利用角度应对气候变化。根据IPCC提供的SRA1B情景下大气环流模式MIROC3.2的输出,利用FAOPenman-Monteith公式计算参考作物腾发量;根据FAO作物系数、SAGE作物分布与柯本气候分类,得到计算单元的作物系数,根据参考作物腾发量与作物系数估算作物需水量;考虑需水与有效降水旬尺度的随机匹配,预测SRA1B情景下未来50年中国各地区主要作物的灌溉需水量。结果表明,参考作物腾发量总体上呈上升趋势,全国平均增加约8%;作物需水量总体上呈增加趋势,东北地区平均增加约10%;灌溉需水量总体上呈增加趋势,东北与华南增加显著。分析表明,SRA1B情景下气温升高是作物需水量增加的主要原因,降水的增加使华北地区灌溉需水量的增加不显著,降水的减少使东北与华南灌溉需水量显著增加。     

气候变化对澜沧江下游梯级电站发电及生态调度的影响

近年来伴随气候变化地表径流呈极端化分布，为水电生态调度带来了挑战。为探究气候变化对电站发电和生态调度的影响、发电和生态目标间协调关系对气候变化的响应，以澜沧江下游梯级电站为例，结合多模式多情景未来径流预估结果及水库发电调度模型，针对发电及生态效益目标实施了单/多目标最优化。结果表明:在气候变化影响下，未来澜沧江径流总量将有所增加，水文变率将显著增强，河道生态所受影响也将增大；电站发电保证率及生态流量破坏率指标受不同调度方案的影响程度较气候变化影响更高，未来发电和生态效益的冲突依然存在；气候变化导致的水文变率增强可加剧发电与生态效益间的冲突，导致保持现有发电效益的同时增大对河道生态的影响。     

气候变化对澜沧江下游梯级电站发电及生态调度的影响

近年来伴随气候变化地表径流呈极端化分布，为水电生态调度带来了挑战。为探究气候变化对电站发电和生态调度的影响、发电和生态目标间协调关系对气候变化的响应，以澜沧江下游梯级电站为例，结合多模式多情景未来径流预估结果及水库发电调度模型，针对发电及生态效益目标实施了单/多目标最优化。结果表明：在气候变化影响下，未来澜沧江径流总量将有所增加，水文变率将显著增强，河道生态所受影响也将增大；电站发电保证率及生态流量破坏率指标受不同调度方案的影响程度较气候变化影响更高，未来发电和生态效益的冲突依然存在；气候变化导致的水文变率增强可加剧发电与生态效益间的冲突，导致保持现有发电效益的同时增大对河道生态的影响。     

Future changes in rainfall,temperature and reference evapotranspiration in the central India by least square support vector machine

Climate change affects the environment and natural resources immensely. Rainfall, temperature and evapotranspiration are major parameters of climate affecting changes in the environment. Evapotranspiration plays a key role in crop production and water balance of a region, one of the major parameters affected by climate change. The reference evapotranspiration or ET₀ is a calculated parameter used in this research. In the present study, changes in the future rainfall, minimum and maximum temperature, and ET₀ have been shown by downscaling the HadCM3 (Hadley Centre Coupled Model version 3) model data. The selected study area is located in a part of the Narmada river basin area in Madhya Pradesh in central India. The downscaled outputs of projected rainfall, ET₀ and temperatures have been shown for the 21st century with the HADCM3 data of A2 scenario by the Least Square Support Vector Machine (LS-SVM) model. The efficiency of the LS-SVM model was measured by different statistical methods. The selected predictors show considerable correlation with the rainfall and temperature and the application of this model has been done in a basin area which is an agriculture based region and is sensitive to the change of rainfall and temperature. Results showed an increase in the future rainfall, temperatures and ET₀. The temperature increase is projected in the high rise of minimum temperature in winter time and the highest increase in maximum temperature is projected in the pre-monsoon season or from March to May. Highest increase is projected in the 2080s in 2081–2091 and 2091–2099 in maximum temperature and 2091–2099 in minimum temperature in all the stations. Winter maximum temperature has been observed to have increased in the future. High rainfall is also observed with higher ET₀ in some decades. Two peaks of the increase are observed in ET₀ in the April–May and in the October. Variation in these parameters due to climate change might have an impact on the future water resource of the study area, which is mainly an agricultural based region, and will help in proper planning and management.     

Irrigated area determination: a case study in the Province of San Juan,Argentina

Much of the central-western region of Argentina, where San Juan Province is located, experiences arid to semi-arid climatic conditions with low average annual rainfall accompanied by substantial evapotranspiration. Consequently, a viable crop industry depends to a large extent upon irrigation from major river systems. Increasing demand for water in the lower basin of the San Juan River is emphasizing the need for more accurate estimates of water used for irrigation. Since the water demand for a particular crop is very closely related to crop area, monitoring the area of crop under irrigation is considered a proxy for the amount of water used. Landsat 5 imagery for the growing season, field data and aerial photographs were used to evaluate crop area.     

Future climate change impact evaluation on hydrologic processes in the Bharalu and Basistha basins using SWAT model

Urbanisation and climate change can have adverse effects on the streamflow and water balance components in river basins. This study focuses on the understanding of different hydrologic responses to climate change between urban and rural basins. The comprehensive semi-distributed hydrologic model, SWAT (Soil and Water Assessment Tool), is used to evaluate how the streamflow and water balance components vary under future climate change on Bharalu (urban basin) and Basistha (rural basin) River basins near the Brahmaputra River in India based on precipitation, temperature and geospatial data. Based on data collected in 1990–2012, it is found that 98.78% of the water yield generated for the urban Bharalu River basin is by surface runoff, comparing to 75% of that for the rural Basistha basin. Comparison of various hydrologic processes (e.g. precipitation, discharge, water yield, surface runoff, actual evapotranspiration and potential evapotranspiration) based on predicted climate change scenarios is evaluated. The urban Bharalu basin shows a decrease in streamflow, water yield, surface runoff, actual evapotranspiration in contrast to the rural Basistha basin, for the 2050s and 2090s decades. The average annual discharge will increase a maximum 1.43 and 2.20 m³/s from the base period for representative concentration pathways (RCPs) such as 2.6 and 8.5 pathways in Basistha River and it will decrease a maximum 0.67 and 0.46 m³/s for Bharalu River, respectively. This paper also discusses the influence of sensitive parameters on hydrologic processes, future issues and challenges in the rural and urban basins.     

Assessing climate change impacts on river hydrology – A case study in the Western Ghats of India

The objective of this study is to evaluate the hydrological impacts of climate change on rainfall, temperature and streamflow in a west flowing river originating in the Western Ghats of India. The long-term trend analysis for 110 yr of meteorological variables (rainfall and temperature) was carried out using the modified Mann–Kendall trend test and the magnitude of the trend was quantified using the Sen’s slope estimator. The Regional Climate Model (RCM), COordinated Regional climate Downscaling EXperiment (CORDEX) simulated daily weather data of baseline (1951–2005) and future RCP 4.5 scenarios (2006–2060) were used to run the hydrological model, Soil and Water Assessment Tool (SWAT), in order to evaluate the effect of climate change on rainfall, temperature and streamflow. Significant changes were observed with regard to rainfall, which have shown decreasing trend at the rate of 2.63 mm per year for the historical and 8.85 mm per year for RCP 4.5 future scenarios. The average temperature was found to be increasing at \(0.10\,^{\circ }\hbox {C}\) per decade for both historical and future scenarios. The impact of climate change on the annual streamflow yielded a decreasing trend at the rate of \(1.2\,\hbox {Mm}^{3}\) per year and 2.56 \(\hbox {Mm}^{3},\) respectively for the past and future scenarios. The present work also investigates the capability of SWAT to simulate the groundwater flow. The simulated results are compared with the recession limb of the hydrograph and were found to be reasonably accurate.     

Climate and water budget change of a Mediterranean coastal watershed, Ravenna, Italy

It is generally difficult to quantify exactly the freshwater going in or out of the coastal watersheds along the northern Adriatic Sea because, on one hand, excess water is drained and pumped into the sea to prevent flooding but, on the other hand, water is brought onto the land from far away for irrigation. Fragmentation of water authorities makes it difficult to collect all the necessary information. Climate change and increasing salinization of the coastal aquifers make it imperative, however, to better know the quantities of freshwater involved in these small basins. The water budget of a small coastal agricultural watershed along the Adriatic Sea in Italy (The Quinto Basin near Ravenna) is presented here considering different land uses. The evaporation of open water and the evapotranspiration of wetlands, pine forests, bare soil and irrigated agriculture are calculated based on the Penman–Monteith equation and the Cropwat program. The current water budget is based on average climate data from 1989 to 2008 and drainage and irrigation data. Predictions for future evapotranspiration, net irrigation and hydrologic deficit are calculated with climate data from IPCC (The Fourth Assessment Report (AR4) 200, Climate change 2007). From the study results, the soil type may determine whether or not a crop will need more or less irrigation in the future. Regulations on land use should therefore consider which crop type can be grown on a specific soil type. Water budget analysis in scenarios A1b and A2 both show an increase of water deficits in the summer and an increase of water surplus in the winter. This is explained by the fact that a larger percentage of the rain will fall in winter and not during the growth season. The open water evaporation will decrease under future climate scenarios as a result of increased relative humidity in winter and decreased wind velocity. This may have a positive effect on the water cycle. The current irrigation is very abundant, but has beneficial effects in contrasting soil salinization and saltwater intrusion into the coastal aquifer.     

West Nile virus in American crows (Corvus brachyrhynchos) in Canada: projecting the influence of climate change

The present study examined the influence of climate change on the spread of West Nile virus (WNV) in Canada among American crows (Corvus brachyrhynchos) by first identifying the significant climatic and environmental determinants of positive WNV cases in American crow specimens from 2009 to 2013. Using this information, we projected climate change scenarios on the potential spread of WNV in American crow species in Canada for three time periods: 2015–2039, 2040–2069, and 2070–2099. Using bird specimen, meteorological and land-use data, the statistical association between positive WNV cases in American crows and the environment was assessed by means of a general linear mixed model. Statistical results revealed that temperature and precipitation were significantly related to positive cases of WNV in American crows. Thus, climate change projections of summer mean temperature averages were projected for the three time periods. Climate change scenarios were created and imported into Quantum Geographic Information System (QGIS) and an algorithm was applied using the raster calculator to spatially delineate current and future areas of risk. Spatial analyses revealed that increased warming in the near future may increase the latitudinal extension of WNV in American crows in Canada.     

Vision 2020: Towards an environmentally sound and sustainable development of freshwater resources in Malaysia

Malaysia has a climate of high humidity, high temperature and abundant rainfall. Rivers supply about 97% of the country's total water needs while ground water accounts for the rest. About 40% of the treated water is lost through man-caused leakages. With a population of 18.3 million people, the total annual domestic, industrial and irrigation water demand is about 11.6 x 106 MI. This figure is projected to rise to 15.2 x 106 MI by year 2000. At present, the total daily water demand is about 4,979 MI and the production capacity is 6,513 MI. Water use and misuse now strain the nation's fragile aquatic environment and natural ecosystems. Current water resource management priorities include water quality improvement, river rehabilitation to restore over-channalized or polluted rivers and development of the inland fisheries potential especially in large man-made reservoirs. A River Basin Information System has been developed to provide integrated information on catchment characteristics, landuse, population and socio-economic profile, river flow, pollution sources, water quality classification, and aquatic biota. Vision 2020 challenges call for a long-term perspective in inland water resource management. Critical post-audits of largescale development and strategic research aimed at alternative and interacting patterns of landwater use are urgently needed.     

Episodic recharge and climate change in the Murray-Darling Basin, Australia

In semi-arid areas, episodic recharge can form a significant part of overall recharge, dependant upon infrequent rainfall events. With climate change projections suggesting changes in future rainfall magnitude and intensity, groundwater recharge in semi-arid areas is likely to be affected disproportionately by climate change. This study sought to investigate projected changes in episodic recharge in arid areas of the Murray-Darling Basin, Australia, using three global warming scenarios from 15 different global climate models (GCMs) for a 2030 climate. Two metrics were used to investigate episodic recharge: at the annual scale the coefficient of variation was used, and at the daily scale the proportion of recharge in the highest 1% of daily recharge. The metrics were proportional to each other but were inconclusive as to whether episodic recharge was to increase or decrease in this environment; this is not a surprising result considering the spread in recharge projections from the 45 scenarios. The results showed that the change in the low probability of exceedance rainfall events was a better predictor of the change in total recharge than the change in total rainfall, which has implications for the selection of GCMs used in impact studies and the way GCM results are downscaled.     

Changes in Habitat Availability for Multiple Life Stages of Diamondback Terrapins (<Emphasis Type="Italic">Malaclemys terrapin</Emphasis>) in Chesapeake Bay in Response to Sea Level Rise

Global sea level rise (SLR) will significantly alter coastal landscapes through inundation and erosion of low-lying areas. Animals that display area fidelity and rely on fringing coastal habitats during multiple life stages, such as diamondback terrapins (Malaclemys terrapin Schoepff 1793), are likely to be particularly vulnerable to SLR-induced changes. We used a combination of empirical nest survey data and results from a regional SLR model to explore the long-term availability of known nesting locations and the modeled availability of fringing coastal habitats under multiple SLR scenarios for diamondback terrapin in the MD portion of Chesapeake Bay and the MD coastal bays. All SLR scenarios projected the rapid inundation of historically used nesting locations of diamondback terrapins with 25%–55% loss within the next 10 years and over 80% loss by the end of the century. Model trajectories of habitat losses or gains depended on habitat type and location. A key foraging habitat, brackish marsh, was projected to decline 6%–94%, with projections varying spatially and among scenarios. Despite predicted losses of extant beach habitats, future gains in beach habitat due to erosion and overwash were projected to reach 40%–600%. These results demonstrate the potential vulnerability of diamondback terrapins to SLR in Chesapeake Bay and underscore the possibility of compounding negative effects of SLR on animals whose habitat requirements differ among life stages. More broadly, this study highlights the vulnerability of species dependent on fringing coastal habitats and emphasizes the need for a long-term perspective for coastal development in the face of SLR.     

Effect of irrigation pumpage during drought on karst aquifer systems in highly agricultural watersheds: example of the Apalachicola-Chattahoochee-Flint river basin,southeastern USA

In the Apalachicola-Chattahoochee-Flint (ACF) river basin in Alabama, Georgia, and Florida (USA), population growth in the city of Atlanta and increased groundwater withdrawal for irrigation in southwest Georgia are greatly affecting the supply of freshwater to downstream regions. This study was conducted to understand and quantify the effect of irrigation pumpage on the karst Upper Floridan Aquifer and river–aquifer interactions in the lower ACF river basin in southwest Georgia. The groundwater MODular Finite-Element model (MODFE) was used for this study. The effect of two drought years, a moderate and a severe drought year, were simulated. Comparison of the results of the irrigated and non-irrigated scenarios showed that groundwater discharge to streams is a major outflow from the aquifer, and irrigation can cause as much as 10 % change in river–aquifer flux. The results also show that during months with high irrigation (e.g., June 2011), storage loss (34 %), the recharge and discharge from the upper semi-confining unit (30 %), and the river–aquifer flux (31 %) are the major water components contributing towards the impact of irrigation pumpage in the study area. A similar scenario plays out in many river basins throughout the world, especially in basins in which underlying karst aquifers are directly connected to a nearby stream. The study suggests that improved groundwater withdrawal strategies using climate forecasts needs to be developed in such a way that excessive withdrawals during droughts can be reduced to protect streams and river flows.     

Impact of climate change on irrigation requirements in terms of groundwater resources

Climate change affects not only water resources but also water demand for irrigation. A large proportion of the world’s agriculture depends on groundwater, especially in arid and semi-arid regions. In several regions, aquifer resources face depletion. Groundwater recharge has been viewed as a by-product of irrigation return flow, and with climate change, aquifer storage of such flow will be vital. A general review, for a broad-based audience, is given of work on global warming and groundwater resources, summarizing the methods used to analyze the climate change scenarios and the influence of these predicted changes on groundwater resources around the world (especially the impact on regional groundwater resources and irrigation requirements). Future challenges of adapting to climate change are also discussed. Such challenges include water-resources depletion, increasing irrigation demand, reduced crop yield, and groundwater salinization. The adaptation to and mitigation of these effects is also reported, including useful information for water-resources managers and the development of sustainable groundwater irrigation methods. Rescheduling irrigation according to the season, coordinating the groundwater resources and irrigation demand, developing more accurate and complete modeling prediction methods, and managing the irrigation facilities in different ways would all be considered, based on the particular cases.     

Surface irrigation performance of date palms under water scarcity in arid irrigated lands

In this paper, a study on the performance of surface irrigation of date palms in a Tunisian arid area (Douz oasis) is presented. The study is conducted in 16 plots with various sizes and soil textures over a 4-year period (2012–2015). In the first step, an assessment of total water requirements of the date palms is carried out. Then, the surface irrigation performance is analyzed using three indicators, i.e., the relative water supply (RWS) indicator, the uniformity index of water distribution (D _U ), and the water application efficiency (E _a ). Finally, the irrigation management problems are identified. The results indicate that in the arid Tunisian Saharan oases, the soil texture, plot size, and farmers’ practices (especially irrigation duration) have significant effects on surface irrigation performance. The average annual net irrigation requirements of date palms are about 2400 mm. The RWS increases from 1.8 in the smaller plots (0.5 ha) to 3.6 in the largest plots (2.5 ha), implying that the increase in the plot size requires an excessive water supply. D _U decreases from 80.7 in the 0.5 ha plots to 65.4 in the 2.5 ha plots; however, no significant difference in the E _a is observed. The results show that the soil texture has no influence on the RWS and D _U , but the E _a is significantly higher in the loamy-sand soils (46.7%) compared to the sandy soils (36.3%). Overall, RWS indicator is higher than 1 (RWS?=?2.6) implying excessive irrigation supply to the system. Although D _U is relatively uniform (>?60%), E _a is relatively low (<?50%) indicating that the current irrigation management is inefficient. These findings have a paramount importance for improving irrigation water management in the Tunisian Saharan oases.     

Long-term seasonal rainfall forecasting: efficiency of linear modelling technique

Using the lagged (past) climate indices, including El Nino–Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) as input parameters and long-term spring rainfall as outputs, calibration and validation of the linear multiple regression (MR) models have been performed. Since Australian rainfall varies both temporally and spatially, the analysis on the linear MR models was performed on regional scale. These models show the capability of linear MR technique for long-term predictions of Western Australian spring rainfall. The emphasis was given to assess the statistical correlations between Western Australian spring rainfall and dominating large-scale climate modes. The efficiency of linear modelling technique was evaluated to predict seasonal rainfall forecasting. At the same time, the Pearson correlation (R), mean absolute error, root-mean-square error and Willmott index agreement (d) were used to assess the capability of MR models. The models which fulfilled the limits of statistical significances were used for the prediction of future spring rainfall using independent data set. The results indicate that during calibration periods maximum achievable correlations varied from 0.47 to 0.53 for the selected stations. In regard to predict peaks and troughs of rainfall time series, it was found that correlations between predicted and actual peaks varied from 0.82 to 0.94 and between predicted and actual troughs varied from 0.53 to 0.91.     

Implications of climatic variability and climate change for water resources availability and management in West Africa

The paper examines: (a) trends in climatic variations and variability with particular emphasis on rainfall (b) the characteristics of climatic events, including floods and droughts, (c) seasonal variations in river flows, (d) mean annual trends in river flows and discharges, (e) local variations of extremes of rainfall and river discharges, (f) the effects of climatic variability and climate change on ground water variations, (g) the problems of acute shortage of freshwater, and (h) the prevalence of water stress whose characteristics would be worsened with the projected impacts of climate change. The results show that: (i) there are a lot of spatial and temporal variations in the characteristics of rainfall and the hydrological systems locally and regionally, although in general, there have been downward trends in rainfall and increases in water deficits and drought events, (ii) that flood events, which also have impacted adversely in many parts of the region, have also been witnessed. The paper then produces projections for future urban and rural water supplies in Nigeria, which is an epitome of West Africa and examines the two main categories of adaptation measures needed to improve water management, namely, those involving the water supply and water demand systems in the study region. Finally, the paper discusses the need to address a number of mechanisms for implementation of the various adaptation measures including: (a) building capacity and manpower, (b) promoting education and public awareness, (c) public participation and the involvement of stakeholders, (d) the establishment of both national and regional co-operation, and (e) the need for climatic and other environmental data collection and monitoring. This revised version was published online in July 2006 with corrections to the Cover Date.