Assessing the Impacts of Climate Change on Hydrology of the Upper Reach of the Spree River: Germany

The aim of this study was to assess the potential impacts of future climate change on the hydrological response in the upper reach of the Spree River catchment using the Soil and Water Assessment Tool (SWAT). The model was calibrated for ten years (1997–2006) and validated with the data from four years (2007–2010) using average monthly stream flow. The impact of future climate change on precipitation, temperature, evapotranspiration and stream flow was then investigated from two different downscaled climate models (CLM and WETTREG2010) under SRES A1B scenarios for two future periods (2021–2030 and 2041–2050). Besides that, sensitivity analysis was carried out with and without observations, to test robustness of the sensitivity algorithm used in the model. Results of the determination coefficient R² and Nasch-Sutcliff efficiency E_NC were 0.81 and 0.80, respectively, during the calibration; 0.71 and 0.70, respectively, during the validation. Although some parameters were changed their sensitiveness ranking when the model run with observations, the SWAT model was, however, able to predict the top influential parameters without observations. According to 12 realizations from the two downscaled climate models, annual stream flow from 2021–2030 (2041–2050) is predicted to decrease by 39 % (43 %). This corresponds to an increase in annual evapotranspiration from 2021–2030 (2041–2050) of 36 % (38 %). The upper reach of the Spree River catchment will likely experience a significant decrease in stream flow due to the increasing in the evapotranspiration rates. This study could be of use for providing insight into the availability of future stream flow, and to provide a planning tool for this area.     

Long-Term Climatic Variability in Calabria and Effects on Drought and Agrometeorological Parameters

In recent decades a general change in climate has been documented in several locations over the world. Such changes could have significant effects on various environmental scenarios, including water resource management, agriculture, hydrology and ecosystems. The complex topography and coastlines of Mediterranean regions influences the climatic regime exhibiting substantial fine-scale spatial variability. In Italy, the climate is generally becoming warmer and drier, with quite large differences depending on the site and data treatment. In this study a historical set of meteorological data (110 precipitation and 28 temperature series), collected over 1921–2007 in the Calabria region (Southern Italy) was analysed. Several meteorological and agrometeorological indices were selected for whether they could evaluate the potential effects of climate change on water availability for natural vegetation and cultivated plants. The significance of the analysed time series (monthly, seasonal and annual time scales) was evaluated by using statistical trend analysis (Mann-Kendall and t-test). Moreover, the intensities of drought events were determined using the Standardized Precipitation Index (SPI) for the time scales of 3 and 6 months. The analysis highlighted a general decrease in annual precipitation and an increase in drought intensity. At a regional level, yearly precipitation decreased by almost 318 mm/100 years (representing almost 30 % of the yearly mean precipitation in the region). Temperature changes were more complex. On a regional scale, yearly mean minimum temperatures increased by 0.9 °C/100 years and maximum and mean temperatures decreased by 1 °C/100 years and 0.8 °C/100 years, respectively. Due to the asymmetric behaviour of temperatures, there was a decreasing impact on evapotranspiration.     

Assessment of Water Resources Availability and Groundwater Salinization in Future Climate and Land use Change Scenarios: A Case Study from a Coastal Drainage Basin in Italy

The joint effect of changes in climate and land use on the future availability of water resources was assessed under the SRES A1B and A2 climate scenarios as well as five land use scenarios for the 2080–2100 time-frame in an Italian coastal watershed. The study area is a small coastal polder (100 km²) characterized by irrigated agriculture, urban expansion, drainage, quarrying and sensitivity to salt-water intrusion. The hydroclimatic budget and the GALDIT index have been computed for assessing water resources availability and groundwater vulnerability to salinization, respectively. The methodology developed is integrated into a tool based on Excel?, which supported the development of scenarios in participatory processes. The conclusions emerged from the analysis are the following: (1) climate change is more effective than land use change in controlling future freshwater availability and amplifies the imbalance between winter surplus and summer deficits, (2) freshwater availability in the summer will likely be affected by an increase in evaporation from open water surfaces due to increased temperature, whereas winter surplus would increase, (3) the vulnerability of the coastal aquifer to salinization will probably moderately increase but an inherent limitation of the GALDIT index to land use change parameters prevents a sound assessment. Strategies that may be proposed to administrators and stakeholders are based on increasing storage of seasonal water surplus.     

Modelling the Effects of Climate Change on Water Resources in Central Sweden

This article describes investigationsinto the effects of climate change on flow regimes oftwenty-five catchments (from 6 to 1293 km²) incentral Sweden. Hydrological responses of fifteenhypothetical climate change scenarios (e.g.combinations of T = +1, +2 and +4 °C andP = 0, ± 10%, ± 20%) were simulated by a conceptual monthly water balance model. The results suggest thatall the hypothetical climate change scenarios wouldcause major decreases in winter snow accumulation.Significant increase of winter flow and decrease ofspring and summer runoff were resulted from mostscenarios. Attendant changes in actualevapotranspiration were also examined for all climatechange scenarios. Despite the changes in seasonaldistribution of evapotranspiration, the change inannual total evapotranspiration was relatively smallwith the maximum change of 23% compared with the 76%for mean annual snow water equivalent changes and 52%for mean annual runoff changes. Such hydrologicresults would have significant implications on futurewater resources design and management.     

Separation of the Impact of Landuse/Landcover Change and Climate Change on Runoff in the Upstream Area of the Yangtze River,China

Landuse/landcover change (LULCC) and climate change (CC) impacts on streamflow in high elevated catchments are very important for sustainable management of water resources and ecological developments. In this research, a statistical technique was used in combination with the Soil and Water Assessment Tool (SWAT) to the Upstream Area of the Yangtze River (UAYR). Different performance criteria (e.g., R², NSE, and PBIAS) were used to evaluate the acceptability of the model simulation results. The model provided satisfactory results for monthly simulations in the calibration (R²; 0.80, NSE; 0.78 and PBIAS; 22.3%) and the validation period (R²; 0.89, NSE; 0.75 and PBIAS; 19.1%). Major landuse/landcover transformations from 1990 to 2005 have occurred from low grassland to medium grassland (2%) and wetlands (0.9%), bare land to medium grassland (0.2%), glaciers to wetland (16.8%), and high grassland to medium grassland (5.8%). The results show that there is an increase in average annual runoff at the Zhimenda station in UAYR by 15 mm of, which approximately 98% is caused by climate change and only 2% by landuse/landcover change. The changes evapotranspiration are larger due to climate change as compared to landuse/landcover change, particularly from August to October. Precipitation and temperature have increased during these months. On the contrary, there has been a decrease in evapotranspiration and runoff from October to March which depicts the intra-annual variations in the vegetation in the study area.

     

Scenario Assessment of Streamflow Simulation and its Transition Probability in Future Periods Under Climate Change

The effect of climate change on water resources is an important challenge. To analyze the negative effects of this phenomenon and recommend adaptive measures, it is necessary to assess streamflow simulation scenarios and streamflow transition probabilities in future periods. This paper employs the HadCM3 (Hadley Centre Coupled Model, version 3) model to generate climate change scenarios in future periods (2010–2039, 2040–2069, and 2070–2099) and under A2 emission scenarios. By introducing climatic variable time series in future periods to the IHACRES (Identification of unit Hydrographs And Component flows from Rainfall, Evaporation and Streamflow data) hydrological model, long-term streamflow simulation scenarios are produced. By fitting statistically different distributions on runoff produced by using goodness-of-fit tests, the most appropriate statistical distribution for each month is chosen and relevant statistical parameters are extracted and compared with statistical parameters of runoff in the base period. Results show that long-term annual runoff average in the three future periods compared to the period 2000–1971 will decrease 22, 11, and 65 %, respectively. ?Despite the reduction in total runoff volume in future periods compared to the baseline period, the decrease is related to medium and high flows. In low flows, total runoff volumes for future periods compared to the baseline period will increase 47, 41, and 14 %, respectively. To further assess the impact of annual average runoff on flows, it is necessary to examine the correlation of time series using streamflow transition probabilities. To compare the streamflow transition probability in each of the future periods with base period streamflow in each month, streamflow is discretized and performance criteria are used. Results show a low coefficient of correlation and high error indicators.     

Combined Assessment of Climate Change and Socio-Economic Development as Drivers of Freshwater Availability in the South of Portugal

A combined assessment of the potential impacts from climate change (CC) and socio-economic development (SED) on water resources is presented for the most important aquifer in the south of Portugal. The goal is to understand how CC and SED affect the currently large pressures from water consuming and contaminating activities, predominantly agriculture. Short-term (2020–2050) and long-term (2070–2100) CC scenarios were developed and used to build aquifer recharge and crop water demand scenarios, using different methods to account for uncertainty. SED scenarios were developed using bottom-up and top-down methods, and discussed at workshops with farmers and institutional stakeholders in the water sector. Groundwater use was quantified for each scenario. Together with the recharge scenarios, these were run through a calibrated groundwater flow model, to study their individual and joint impacts on groundwater levels and discharge rates into a coastal estuary. Recharge scenarios show clear negative long-term trends and short-term increase in temporal variability of recharge, though short-term model uncertainties are higher. SED scenario 1 (SED1), predicting intensification and decline of small farms, considered the most likely by all workshop participants, shows a large drop in agricultural area and water demand. SED2, a most desired scenario by farmers, foresees growth and modernization of agriculture, but proves unsustainable in combination with predicted CC without efficient adaptation measures. The results thus reveal that CC in the region will dynamically interact with economic factors, and going one step beyond, CC could be directly integrated as a constraint in the development of SED scenarios. Exercises involving the integration of CC and SED regionally based scenarios, constructed in both bottom-up and top- down fashion and discussed in participatory contexts are still rarely used for adaptation, and specifically adaptation of agriculture to water scarcity. The joint analysis of CC and SED revealed challenging, as it involved the use of different methods across the border between natural and social sciences. In our view this method contributes in an encouraging manner to a more holistic and transdisciplinary water management, by allowing a more plausible identification of what (and if) adaptation measures are needed.     

Effects of Land-Use and Climate Change on Hydrological Processes in the Upstream of Huai River, China

Land use/land cover and climate change can significantly alter water cycle at local and regional scales. Xixian Watershed, an important agricultural area in the upper reach of the Huaihe River, has undergone a dramatic change of cultivation style, and consequently substantial land use change, during the past three decades. A marked increase in temperature was also observed. A significant monotonic increasing trend of annual temperature was observed, while annual rainfall did not change significantly. To better support decision making and policy analysis relevant to land management under climate change, it is important to separate and quantify the effect of each factor on water availability. We used the Soil and Water Assessment Tool (SWAT), a physically based distributed hydrologic model, to assess the impact of Land use and climate changes separately. The SWAT model was calibrated and validated for monthly streamflow. Nash-Sutcliff efficiency (NSE), percentage bias (PBIAS), and coefficient of determination (R ²) were 0.90, 6.3 %, and 0.91 for calibration period and 0.91, 6.9 %, and 0.911 for validation period, respectively. To assess the separate effect of land use and climate change, we simulated streamflow under four scenarios with different combinations of two-period climate data and land use maps. The joint effect of land use and climate change increased surface flow, evapotranspiration, and streamflow. Climate variability increased the surface water and stream-flow and decreased actual evapotranspiration; and land use change played a counteractive role. Climate variability played a dominant role in this watershed. The differentiated impacts of land-use/climate variabilities on hydrological processes revealed that the unapparent change in stream-flow is implicitly because the effects of climate variability on hydrological processes were offset by the effects of land use change.     

Assessing Impacts of Conservation Measures on Watershed Hydrology Using MIKE SHE Model in the Face of Climate Change

Climate change triggers changes in temperature, precipitation, evapotranspiration, etc. and has a significant impact on water resources in many regions. Considering the increasing scarcity of water as a result of climate change, conservation of water and groundwater recharge have become crucial factors for water resources planning and management. In this paper, an attempt is made to study the detailed hydrological behaviour of a treated watershed using physically based distributed hydrological modelling system MIKE SHE to assess the impact of conservation measures on watershed hydrology considering future climate change. Three hypothetical management scenarios are simulated for the period 2010–2040. RegCM4 regional climate model is used in the study for RCP 4.5 and RCP 8.5 scenarios. Detailed hydrological water balance is extracted for individual years from 1979 to 2009 to compare relevant components. The evaluation for base period shows 10.06% reduction in surface runoff and 11.33% enhancement in groundwater recharge. Further simulation with RCP 4.5 and RCP 8.5 scenarios show notable reduction in surface runoff and increase in groundwater recharge. The structures in the micro-watershed influence the surface runoff and increase infiltration into the soil, resulting in higher groundwater recharge. MIKE SHE simulations for various structures management scenarios establish the role of conservation measures in reducing surface runoff and enhancing groundwater recharge under substantial effect of climate change. The results will assist in decision-making on watershed development plans in quantitative terms, including planning for water conservation measures in the face of climate change.

     

Water Footprint of Grain Product in Irrigated Farmland of China

China faces the dual challenge of grain production pressure and water scarcity. It is significant to reduce water footprint of grain product (WFGP, m³/t) in irrigated farmland. The focus of grain production and agricultural water use, and the precondition is to determine the WFGP and its composition. This paper estimates the WFGP in irrigated farmland of 31 provinces (including municipalities, autonomous regions) a by collecting actual data of 443 typical irrigation districts in 1998, 2005 and 2010, and analyses its temporal and spatial variation in irrigated farmland of China. The result shows that the WFGP in each province decreases with time except in Jiangxi and Hunan, and the average value of all provinces reduced from 1494 m³/t in 1998 to 1243 m³/t in 2010. The WFGP decreases faster in more developed municipal cities and major grain production provinces. The annual average WFGP in irrigated farmland is 1339 m³/t and the blue and green water account for 63.5 % and 36.5 % of the total, respectively. The WFGP and its composition are significantly different between provinces. Generally, provinces distributed inside and beyond Huang-Huai-Hai Plain, have a higher water productivity, lower WFGP and blue water footprint of grain product, while most provinces located in northwest, northeast, southeast and south China have a higher WFGP and lower proportion of green water in the WFGP as a whole. Portion of the blue water footprint (BWFGP) is not consumed for crop evapotranspiration (BWFGP _ET ) but conveyance loss (BWFGP _cl ). The national averaged BWFGP _cl decreases with time and but still remains up to 466 m³/t in 2010, making up 34.8 % of the WFGP. In order to safeguard grain security and ease the water resource pressure, the Chinese government should increase investment and apply advanced technology for developing water-saving agriculture, improve the efficiency of water use and further reduce the WFGP. Considering also the contribution of grain output and the relatively high WFGP, the government should give priority to developing water-saving agriculture in the Northeast of China.     

Groundwater Use for Irrigation and its Productivity: Status and Opportunities for Crop Intensification for Food Security in Bangladesh

Bangladesh has a large and growing population that will demand more food and place greater pressure on resources. Dry season irrigated Boro rice production is important for national food security. Dry season irrigation mainly uses groundwater, but the extent of its use is not well known. We assessed groundwater use and water productivity of Boro in the northwest region of Bangladesh using remote sensing based energy balance modelling, crop classification and secondary statistics. The energy balance modelling shows a large spatial variation in the actual evapotranspiration (ET_a) from about 325 to 470 mm, with an overall spatial average of 365 mm during dry season. The estimated values of ET_a correspond well with independent values from field and regional scale soil and water balance modelling results. From spatial estimates of ET_a and effective rainfall, we computed regional net groundwater use for Boro production in 2009 as 2.4 km³. Groundwater is being used unsustainably in some areas, and a spatial time series (1990 to 2010) of pre- and post-monsoon groundwater depth changes in the northwest region of Bangladesh suggests that, with the current level of groundwater use, falling groundwater levels may pose a long term threat to the sustainability of irrigated agriculture in much of the region. Boro water productivity varies from 0.95 to 1.35 kg/m³, allowing the identification of high performing “bright” and low performing “hot” spots and the development of strategies to reduce crop yield/productivity gaps and ensure future food security.     

Streamflow Trends and Climate Variability Impacts in Poyang Lake Basin, China

Under the background of global warming, does the effect of the rising global surface temperature accelerate the hydrological cycle? To address this issue, we use the hydro-climatic data from five sub-basins in Poyang Lake basin in the southeast China over the past 50 years, to investigate the annual and seasonal trends of streamflow and the correlations between streamflow and climatic variables. The Theil–Sen Approach and the non-parametric Mann–Kendall test are applied to identify the trends in the annual and seasonal streamflow, precipitation and evapotranspiration series. It was found that annual and seasonal streamflow of all the stations had increasing trends except Lijiadu station in wet season. Only 37.5% hydro-stations in annual streamflow increased significantly, while most stations increased at 95% significance level in dry season. Trends in annual and seasonal precipitation during the whole period were generally not as significant as those in evapotranspiration. The correlations between streamflow and climate variables (precipitation and evapotranspiration) were detected by the Pearson’s test. The results showed that streamflow in the Poyang Lake basin are more sensitive to changes in precipitation than potential evapotranspiration.     

Impact of Climate Change on the Hydrological Regime and Water Resources in the Basin of Siatista

This paper examines an assessment of the impact of climate change on hydrological regimes and water resources in the basin of Siatista, a sub-basin of the Aliakmon river basin, located in Northern Greece. Initially all acquired hydrometeorological data of the study area, as well as the hydrometric data at the outlet of the basin, were analyzed and processed. A monthly conceptual water balance model was then calibrated using historical hydrometeorological data for determining changes in streamflow runoff under two different equilibrium scenarios (UKHI, CCC) referring to the years 2020, 2050 and 2100. It was found that by applying the two scenarios there will be a reduction of the mean winter runoff values, a serious reduction of summer runoff, an increase of maximum annual runoff and a decrease of minimum annual runoff values, an increase of potential and actual evapotranspiration, leading to a decrease of soil moisture, a reduction of snow accumulation and melting due to temperature increases, resulting in a decrease of spring runoff values and a shifting of the wet period towards December, resulting in severe prolongation of the dry period.     

Performance Indexes Analysis of the Reservoir-Hydropower Plant System Affected by Climate Change

Assessing the effects of climate change phenomenon on the natural resources, especially available water resources, considering the existing constraints and planning to reduce its adverse effects, requires continuous monitoring and quantification of the adverse effects, so that policymakers can analyze the performance of any system in different conditions clearly and explicitly. The most important objectives of the present research including: (1) calculating the sustainability index for each demand node based on the characteristics of its water supply individually and also calculating the sustainability index of the whole water supply system, (2) investigation the compatible of changes trend among various reservoir performance indexes and (3) evaluation the changes in performance reservoir indexes in the future time period compared to the baseline tie period under three Concentration Pathway (RCP) RCP2.6, RCP4.5 and RCP8.5 scenarios for all water demand nodes and the entire water supply system. To this end, first, climatic parameters data affecting on the water resources such as temperature and precipitation were gathered in the baseline period (1977–2001) and the climatic scenarios were generated for the future period (2016–2040) using the Fifth Assessment Report (AR5) of the International Panel on Climate Change (IPCC). Then, the irrigation demand changes of the agricultural products with the Cropwat model and the value of inflow to the reservoir with the Artificial Neural Network (ANN) model were calculated under the climate change effects. In the next step, the climate change effects on the water supply and demand were simulated using Water Evaluation and Planning model (WEAP), and its results were extracted so as the water management indexes. The results show that the temperature will increase in the future period under all three RCP scenarios (RCP2.6, RCP4.5 and RCP8.5) compared to the baseline period, while precipitation will decrease under the RCP2.6 scenario but will increases under RCP4.5 and RCP8.5 scenarios. Under the trend of changing in temperature and rainfall, the irrigation demand in the agricultural sector in all scenarios will increase compared to the baseline period. However, the inflow of reservoir will decrease under the RCP2.6 and RCP4.5 scenarios and will increases under RCP8.5 scenario. Evaluation of WEAP modeling results shows that the sustainability index of the entire Marun water-energy system will decrease in the future period compared to the baseline period under the RCP2.6, RCP4.5 and RCP8.5 scenarios by 13, 10 and 8%, respectively. The decrease in the system sustainability index shows that in the absence of early planning, the Marun water-energy supply system will face several challenges for meeting the increasing demand of water in different consumer sectors in the coming years.

     

Spatio-Temporal Variation of Water Availability in a River Basin under CORDEX Simulated Future Projections

In the present study, spatio-temporal variability of hydrological components under climate change is analysed over Wainganga River basin, India. In order to address the climate change projection, hydrological modelling is carried out using a macro scale, semi-distributed three (3)-Layer Variable Infiltration Capacity (VIC-3 L) model. The high-resolution (0.5^o?×?0.5^o) meteorological variables are divided into multiple periods to calibrate and validate the VIC-3 L model. The future projections (2020–2094) of the water balance components are achieved using the high resolution hydrological variables from the COordinated Regional Downscaling EXperiment (CORDEX) dataset under Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios. The uncertainty associated with the multi-model projections are evaluated using Reliability Ensemble Averaging (REA) and the bias correction is accomplished with non-parametric quantile mapping. A probabilistic based areal drought index is also computed for different scenarios using Standardized Precipitation Evapotranspiration Index (SPEI). From the results, it is observed that amount of rainfall, evapotranspiration, and runoff has increased over the basin with no change in the spatial pattern. However, temporal variability is noticed with an increasing trend for rainfall and runoff in the non-monsoon season than the monsoon. Streamflow is expected to increase significantly, especially for medium to low flows (those occurring between 0.2 and 0.9 probability of exceedance in a Flow Duration Curve). In addition, the area under the drought condition has decreased under the projected climate scenarios.     

Impact of Urbanization and Climate Change on Aquifer Thermal Regimes

We evaluated the past impacts of urbanization and climate change on groundwater—in particular, aquifer temperature—in the Sendai plain, Japan, and further compared with the probable changes due to changing climate in the future. A series of simulations were performed and matched with the observed temperature-depth profiles as a preliminary step for parameter calibration. The magnitude of ground surface warming estimated from subsurface temperature spans 0.9–1.3°C, which is consistent with the calibrated ground surface warming rates surrounding various observation wells (0.021–0.015°C/year) during the last 60 years. We estimate that approximately 75% of the ground surface temperature change can be attributed to the effect of past urbanization. For the climate predictions, climate variables produced by the UK Hadley Centre’s Climate Model (HadCM3) under the A2, A1B and B1 scenarios were spatially downscaled by the transfer function method. Downscaled monthly data were used in a water budget analysis to account for the variation in recharge and were further applied in a heat transport equation together with the estimated ground surface warming rates in 2080. Anticipated groundwater recharge under the projected climate in 2080 would decrease by 1–26% compared to the 2007 estimates, despite the projected 7–28% increase in precipitation, due to a higher degree of evapotranspiration resulting from a 2.5–3.9°C increase in surface air temperature. The overall results from the three scenarios predict a 1.8–3.7°C subsurface temperature change by 2080, which is notably greater than the previous effect of urbanization and climate change on aquifer temperature in the Sendai plain.     

Inflow of surface and groundwater to Lake Ladoga based on stable isotope (2H, 18O) composition

Stable isotope (deuterium – ²H and oxygen-18 – ¹⁸O) surveys of water in Lake Ladoga and several rivers and small lakes within its watershed were conducted during 2012–2018. Over these 6 years, specific spatial and time differences in water isotope composition of Ladoga and small water bodies and streams were found. These differences depended firstly, on wetland type and the lakes distribution on the watershed and secondly, on groundwater discharge and type of lithological substrate (geological sediments or crystalline rocks). Besides landscape, climate (air temperature, precipitation, evapotranspiration) is a main physical factor which controls all scales of the stable isotope variations. In modern times, the sub-latitudinal gradient of climate but also presence of permafrost in the past effects the stable isotope variation. The isotopic composition divides the tributaries of Ladoga into three groups with a wide range of δ¹⁸O seasonal variations, and a significant atmospheric component. The isotopic composition of Ladoga water is generally stable ranging from δ¹⁸O = ?11.7 to ?9.5‰ (average δ¹⁸O = ?10.6‰), δ²H = ?84 to ?74‰ (average δ²H = ?78‰). The effect of evaporation is clearly seen due to accumulation of deuterium and oxygen-18 and a shift to the right from the Local Meteoric Water Line of δ²H versus δ¹⁸O diagram. In Lake Ladoga there is a local deviation of δ¹⁸O which can be explained by subaqueous discharge of groundwater from Riphean sediments.     

Diagnosing Climate Change and Hydrological Responses in the Past Decades for a Minimally-disturbed Headwater Basin in South China

Identifying the trends of climate and hydrological changes is important for developing adaptive strategies for effective water resources management. Many studies focused on the prediction of future climate at a regional/global scale using General Circulation Models (GCM) or these models’ downscaled outcomes. However, diagnosing historical trends is regarded valuable for local areas, especially considering the spatial heterogeneity (both occurrence and magnitude) of climate change and uncertainty of climate projection. In this study, we selected the headwater area of the East River Basin in South China, which has minimal human-induced disturbance, to detect climate change and its hydrological changes over a past 50-year (1955–2004) time period. Although the climate warming agreed with the global situation, its magnitude was small and no sign of intensified rainfall or change of annual rainfall was found. Nevertheless, no-rain days increased and light-rain days decreased, indicating a longer dry interval between rainfall events. There was a significant downtrend of wind speed with a substantial reduction in magnitude, resulting in a decrease in the estimated potential evapotranspiration and a slight increase in the soil water content. Risks of flooding may not be a big concern, but water availability may be affected marginally in May and June due to the decreased rainfall and increased no-rain days. Overall, our results can improve the understanding of climate change and help watershed managers take precautions when facing climate change. This study also implies the necessity of investigating climate change at a local scale and at different time scales.     

Climate Change and Resource Management in the Columbia River Basin

Abstract

Scenarios of global climate change were examined to see what impacts they might have on transboundary water management in the Columbia River basin. Scenario changes in natural streamflow were estimated using a basin hydrology model. These scenarios tended to show earlier seasonal peaks, with possible reductions in total annual flow and lower minimum flows. Impacts and adaptation responses to the natural streamflow scenarios were determined through two exercises: (a) estimations of system reliability using a reservoir model with performance measures and (b) interviews with water managers and other stakeholders in the Canadian portion of the basin. Results from the two exercises were similar, suggesting a tendency towards reduced reliability to meet objectives for power production, fisheries, and agriculture. Reliability to meet flood control objectives would be relatively unchanged in some scenarios but reduced in others. This exercise suggests that despite the high level of development and management in the Columbia, vulnerabilities would still exist, and impacts could still occur in scenarios of natural streamflow changes caused by global climate change. Many of these would be indirect, reflecting the complex relationship between the region and its climate.     

Sensitivity Analysis of Coupled Hydro-Economic Models: Quantifying Climate Change Uncertainty for Decision-Making

The paper assessed the sensitivity of an integrated hydro-economic model, to provide a quantitative range of uncertainty in the impacts of climate change on water balance components and water use in the agricultural sector of Apulia region located in a semi-arid Mediterranean climate area in southern Italy. Results show that the impacts of climate change are expressed in the future by an increase in the net irrigation requirements (NIRs) of all crops. Total cultivated land is reduced by 8.5 % in the future, and the percentage of irrigated land decreases from 31 to 22 % of total agricultural land. Reduction in the irrigated land, together with the variation in the cropping pattern and the adoption of the different irrigation techniques, led to a decrease in water demand for irrigation across the entire region. The sensitivity analysis shows that the groundwater recharge has the lowest correlation to climatic parameters. Results are addressed to the scientific community and decision makers to support the design of adequate adaptation policies for efficient water management under the severe drought conditions that are likely to occur in the region according to climate change projections.