Water Resources Management Strategies Research Articles

Drought Cycle Analysis to Evaluate the Influence of a Dense Network of Small Reservoirs on Drought Evolution

AbstractDrought‐affected regions often contain high densities of small reservoirs, usually informally built, as drought‐coping mechanism. These structures influence socio‐hydrological dynamics and have the potential to alter hydrological processes relevant to drought emergence and development. This study aimed to analyze the influence of a high concentration of small reservoirs on the intensification and evolution of drought events. We present an innovative method, which we call “Drought Cycle Analysis”, that tracks the concomitance of precipitation and water storage deficit and associates this with four drought stages: Wet Period, Meteorological drought, Hydro‐meteorological drought and Hydrological drought period. The methodology was tested for the Riacho do Sangue River watershed located in the semi‐arid region of northeast Brazil. We used a combination of satellite imagery (Landsat 5, 7 and 8) and an empirical equation to estimate the volume stored in the dense network of small reservoirs. Using the Drought Cycle Analysis, we show that the unmonitored small reservoirs induced and modified drought events, extending the duration of hydrological drought on average by 30%. Furthermore, this extension can double for specific drought events. The Drought Cycle Analysis method proved useful for monitoring and comparing the evolution of different drought events, in addition to being applicable as an auxiliary tool in the improvement of water resources management of large reservoirs. This study demonstrates the importance of considering small reservoirs in water resource management strategy development for drought‐prone regions.

Management of Water Resources in the Semiarid Region of Rio Grande do Norte: a case study on the municipality of Lucrécia

This research aimed to identify water resources management strategies in extreme drought event scenarios in the municipality of Lucrécia, in the state of Rio Grande do Norte (RN), in the period 2012 to 2018. As a methodological procedure, a bibliographical and documentary, in addition to field research, with interviews with municipal managers and residents. A photographic record of the study area was also carried out. It was found that, in the city, there is a folder dedicated to water resources that guides water management and is the basis for the adoption of measures aimed at municipal supply in times of difficult access to water, due to the reduction in water availability. It was observed that part of the interviewed population understands the drought as responsible for the difficulties faced in the city, mainly about the reduction of the water level in the reservoir. It was found that, of the 52 towns belonging to the hydrographic basin of the Apodi-Mossoró river, only 10 participate in the meetings of the basin committee, the municipality of Lucrécia does not have representatives on the Committee. This finding deserves special consideration since water and the administration of its multiple applications are generators of conflicts, it highlights the importance of understanding how municipalities in the Semiarid region carry out the management of water resources and how they understand the challenges of coexistence with its area, aiming at the sustainable use of water.

Spatiotemporal Trend Analysis of Temperature and Rainfall over Ziway Lake Basin, Ethiopia

Rainfall and temperature trends detection is vital for water resources management and decision support systems in agro-hydrology. This study assessed the historical (1983–2005) and future (2026–2100) rainfall, maximum temperature (Tmax), and minimum temperature (Tmin) trends of the Ziway Lake Basin (Ethiopia). The daily observed rainfall and temperature data at eleven stations were obtained from the National Meteorological Agency (NMA) of Ethiopia, while simulated historical and future climate data were obtained from the Coupled Model Intercomparison Project 5 (CMIP5) datasets under Representative Concentration Pathways (RCP) of 4.5 and 8.5. The CMIP5 datasets were statistically downscaled by using the climate model data for hydrologic modeling (CMhyd) tool and bias corrected using the distribution mapping method available in the CMhyd tool. The performance of simulated rainfall, Tmax, and Tmin of the CMIP5 models were statistically evaluated using observation datasets at eleven stations. The results showed that the selected CMIP5 models can reasonably simulate the monthly rainfall, Tmax, and Tmin at the majority of the stations. Modified Mann–Kendall trend test were applied to estimate the trends of annual rainfall, Tmax, and Tmin in the historical and future periods. We found that rainfall experienced no clear trends, while Tmax, and Tmin showed consistently significant increasing trends under both RCP 4.5 and 8.5 scenarios. However, the warming is expected to be greater under RCP 8.5 than RCP 4.5 by the end of the 21st century, resulting in an increasing trend of Tmax and Tmin at all stations. The greatest warming occurred in the central part of the basin, with statistically significant increases largely seen by the end of the 21st century, which is expected to exacerbate the evapotranspiration demand of the area that could negatively affect the freshwater availability within the basin. This study increases our understanding of historic trends and projected future change effects on rainfall- and evapotranspiration-related climate variables, which can be used to inform adaptive water resource management strategies.

Identification of rainfall homogenous regions in Saudi Arabia for experimenting and improving trend detection techniques

In Saudi Arabia, identifying homogenous zones based on rainfall patterns is critical for ensuring a predictable and stable water resource and agriculture management strategy. As a result, the present research aims to identify Saudi Arabia's homogeneous rainfall zones and examine rainfall patterns in these areas. By proposing a novel trend analysis technique with a particular graphical representation, this study utilises and compares the traditional Mann-Kendall (MK) test, modified MK test, and basic Sen-innovative trend analysis (ITA) method. Another approach is to use the Pettit change point test to objectively identify subcategories as "low" or "high." The applications are based on 40-year rainfall records from 22 Saudi Arabian meteorological sites. K-means clustering and hierarchical clustering on principle component analysis (HCPC) were used to find homogeneous areas. The results of the homogeneous region identification revealed that the research area is divided into three clusters, each with three distinct climatic characteristics. Cluster 1 contains eight stations, whereas clusters 2 and 3 each have seven. The results of trend identification utilising the MK, MMK, and ITA tests revealed that cluster 1 had a falling rainfall trend, whereas cluster 2 had a very minor decreasing and increasing rainfall trend. Cluster 2 can be thought of as a transition zone. Cluster 3 observedan upward trend in rainfall. While the proposed new form of ITA produced similar results with more detailed analysis such as change point-based high and low value identification, and magnitude of decreasing and increasing trend, the proposed new form of ITA produced similar results with more detailed analysis such as change point-based high and low value identification. This study will serve as a foundation for future work by scientists and planners on the identification of climatic zones, the development of trend detection techniques, and the formulation of water resource management strategies.

Spatio-temporal variability of climatic parameters across different altitudes of North- Western Himalaya

Climate change impact varies across different altitudinal ranges and demands local specific management strategies for water resource and farming system management. The present study analyses spacio-temporal climate parameters across different altitudes of Himachal Pradesh a hilly state of India. Analysis shows that annually, minimum temperature has significantly decreased by -0.09°C at altitude I (350 - 400 m) while maximum temperature has significantly increased by 0.05°C at altitudes I and II (1400-1500 m) and decreased significantly by -0.08°C at altitude III (2000- 2100 m). Higher regions Altitude – IV (2900-3000 m) received lowest rainfall (746.1 mm) with 30.2 % variation. Seasonal rainfall variability was higher in post monsoon (102 - 174%) and least in monsoon (21 - 57%). Annual rainfall at altitude I is strongly irregular (PCI 20.1 to 22.3), followed by altitude – IV (PCI 15-25); altitude – II irregular (PCI 15-20) and altitude – III moderate to irregular (PCI 12 -19) rainfall. Seasonal Index values for four altitudes fall between 0.91-0.96 revealed that rainfall is irregular and markedly seasonal with longer drier season. Higher wavelet powers in altitude - I and II after 2005 suggests frequency of extreme rainfall occurrence had increased.

Estimating potential yield and change in water budget for wheat and maize across Huang-Huai-Hai Plain in the future

Climate change impacts crop productivity as atmospheric conditions and water supply change, particularly in intensive cropping areas. This study used the validated AquaCrop Model, which was run with downscaled daily climate data produced by SDSM and CanESM2. The changes in the potential grain yield of winter wheat and summer maize and water budget during the cropping seasons were estimated for the Huang-Huai-Hai Plain (3H Plain) under RCP4.5 and RCP8.5 scenarios. The results show that the potential yield of winter wheat is increasing with similar spatial patterns in the 2030s, 2050s, and 2080s, with much of the increase is distributed in Shandong and northeastern parts of Henan. During the winter wheat growth period, the water budget deficit will likely improve from −210 mm in the 2030s to −202 mm in 2080s under RCP4.5 and from −206 mm in the 2030s to −191 mm in 2080s under RCP8.5 across the 3H Plain. The water budget during the winter wheat period will continue to be in deficit in the north 3H Plain and improvements are estimated mostly in the lower southern areas of the Plain. The summer maize potential yield is estimated to increase from the baseline period, but yields will decrease by 0.81%, 1.19%, and 2.10% in the 2030s, 2050s, and 2080s, respectively, under RCP8.5 compared to RCP4.5. During the summer maize growth period, the water budget is also estimated to improve from 109 mm in 2030s to 126 mm in 2080s under RCP4.5 and 107 mm in the 2030s to 163 mm in 2080s under RCP8.5. This increase is mainly estimated in the central and south of the 3H Plain. The estimated ETc of winter wheat shows no significant decrease, while the reduction of 6 mm and 13 mm for summer maize is observed under RCP4.5 and RCP8.5, respectively. The study provides scientific evidence to devise adaptation and mitigation climate change strategies for agricultural productivity and water resource management.

Climate change and groundwater resources availability in the Great Limpopo National Park (Mozambique): the current state of knowledge

This work outlines a comprehensive study of groundwater resources supply in Mozambique’s Great Limpopo National Park buffer zone in Southern Africa. To protect biological diversity and the water resources supply of dispersed communities of the buffer zone is a crucial problem to fix people in the region and, in the meantime, to boost the development of the Limpopo National Park. This work shows the current state of knowledge about this topic and try to point out some suggestions on technical solutions. Some previous studies concluded that two different main factors make a complex water supply in this area: (i) the rainwater distribution, it is hard to transform the rainwater into groundwater resources available for exploitation, and (ii) the common groundwater resources, rich in elements such as Boron (B), Mercury (Hg), Uranium (U), Zinc (Zn) and Lead (Pb). The occurrence of these elements is linked to the presence of groundwater with long residence times, unsafe for people’s health. The methodological approach adopted has been to assess the potential infiltration, applying the inverse hydrogeological budget technique, starting from the main outcropping geological units, in the study area. Due to the lack of meteorological data referred to Limpopo National Park, the gauge stations located in the Kruger National Park during the last 64 years have been, on the whole, considered. The target of the study has been to assess the trend of meteorological data and understand how precipitations could affect groundwater recharge and their availability. Without a strategy of biodiversity conservation and sustainable water resources management, they cannot be reached and guaranteed healthy conditions for local dispersed communities. A hydrogeoethical responsible approach is essential to protect biological diversity and hydrosocial cycle framework with integrative ecosystem services and nature-based solutions.

Sources and behaviors of dissolved sulfate in the Jinan karst spring catchment in northern China identified by using environmental stable isotopes and a Bayesian isotope-mixing model

In recent decades, surface water and groundwater in the Jinan spring catchment have become increasingly contaminated by sulfate due to the expansion of urbanization and the increasing intensity of anthropogenic activities. In this study, ten surface water samples and forty-three groundwater samples were collected in the catchment from June to September 2019, and their hydrochemistry and stable isotopes (δ34SSO4, δ18OSO4, δDH2O and δ18OH2O) combined with a Bayesian isotope mixing model were used to identify sources and transformations and to quantitatively evaluate the contribution of sulfate from multiple potential sources of pollution. The dual isotopes of sulfate and the isotope mixing model showed that sulfate in the surface water was mainly derived from evaporite dissolution (32.6%), sewage (18.8%), soil sulfate (15.4%) and sulfide oxidation (10.2%), while that in the groundwater was mainly derived from soil sulfate (32.4%) and sewage (30.6%). In groundwater, the proportions of sewage and evaporite dissolution increased from the indirect recharge area to the discharge area, while the contribution of soil sulfate and sulfide oxidation decreased. In regard to surface waters, the contribution proportion of evaporite dissolution to SO42− in June was 40.9%, which was significantly higher than 24.2% in September, but the proportion of sewage, soil sulfate and sulfide oxidation was lower in June (13.7, 12.9 and 9.5%, respectively) than in September (23.8, 17.8 and 10.8%, respectively). There was no significant correlation between the ratio of SO42−/Cl− and δ34SSO4 and δ18OSO4 in surface water and groundwater, indicating that bacterial sulfate reduction did not play a major role. This study can provide a reference for the development of effective pollution management strategies for water resources in karst areas of northern China.

An accuracy-improved flood risk and ecological risk assessment in an interconnected river–lake system based on a copula-coupled hydrodynamic risk assessment model

Understanding flood event-related risk in an interconnected river–lake system (IRLS) is a prerequisite for developing water resource management strategies and enhancing disaster resilience. Previous flood event-related risk assessments either hardly consider the context in which water diversion encounters flood events or hardly consider the physical process, stochastic analysis and multivariate interactions of flood event characteristics simultaneously, thereby resulting in a less reliable assessment of flood event-related risk. To resolve this limitation, a copula-coupled hydrodynamic risk assessment model (CHRAM) is proposed to characterize the physical, multivariate, and stochastic nature of risk, improving the accuracy of risk assessment. In this study, CHRAM is capable of accurately quantifying flood event-related risks (i.e., flood risk and ecological risk) of the Nansi Lake Basin in the flood season under the operation of the eastern route of the South-to-North Water Diversion Project in China. Our findings revealed that the total flood volume (Rsum) and duration (Td) of flood events were significantly sensitive characteristic indexes for flood risk and ecological risk. In addition, the security domains of flood risk (Rsum < 35 mm and Td < 23 d) and ecological risk (Rsum < 50 mm and Td < 27 d) were determined based on the analysis of the relationship between sensitive characteristic indexes and risk indicators. The results also showed that the impact of Td on flood risk, ecological risk and flood-ecological combined risk was 3–14 times greater than the impact of Rsum. The occurrence probability of flood-ecological combined risk was smaller than that of flood risk but greater than that of ecological risk, with the corresponding maximum risk probabilities of 11.2%, 36.5%, and 4.7%, respectively. This study extends the current knowledge about risk assessment in IRLS and is beneficial to instruct the management of projects for similar systems.

Changes in streamflow regimes and their responses to different soil and water conservation measures in the Loess Plateau watersheds, China

AbstractInvestigating the changes in streamflow regimes in response to various influencing factors contributes to our understanding of the mechanisms of hydrological processes in different watersheds and to water resource management strategies. This study examined streamflow regime changes by applying the indicators of hydrologic alteration method and eco‐flow metrics to daily runoff data (1965–2016) from the Sandu, Hulu and Dali Rivers on the Chinese Loess Plateau, and then determined their responses to terracing, afforestation and damming. The Budyko water balance equation and the double mass curve method were used to separate the impacts of climate change and human activities on the mean discharge changes. The results showed that the terraced and dammed watersheds exhibited significant decreases in annual runoff. All hydrologic metrics indicated that the highest degree of hydrologic alteration was in the Sandu River watershed (terraced), where the monthly and extreme flows reduced significantly. In contrast, the annual eco‐deficit increased significantly, indicating the highest reduction in streamflow among the three watersheds. The regulation of dams and reservoirs in the Dali River watershed has altered the flow regime, and obvious decreases in the maximum flow and slight increases in the minimum flow and baseflow indices were observed. In the Hulu River watershed (afforested), the monthly flow and extreme flows decreased slightly and were categorized as low‐degree alteration, indicating that the long‐term delayed effects of afforestation on hydrological processes. The magnitude of the eco‐flow metrics varied with the alteration of annual precipitation. Climate change contributed 67.47% to the runoff reduction in the Hulu River watershed, while human activities played predominant roles in reducing runoff in the Sandu and Dali River watersheds. The findings revealed distinct patterns and causes of streamflow regime alteration due to different conservation measures, emphasizing the need to optimize the spatial allocation of measures to control soil erosion and utilize water resources on the Loess Plateau.

Groundwater quality evaluation and health risk assessment in coastal lowland areas of the Mekong Delta, Vietnam

This study provides a comprehensive assessment of groundwater quality in the Mekong Delta (Vietnam) and their potential risks to human health. The dataset consists of 282 groundwater samples collected in dry and rainy seasons between 2017 and 2018. Multiple physio-chemical parameters, groundwater quality index (GWQI), and irrigation water quality indices (IWQI) were employed to evaluate the suitability of groundwater resources for drinking and irrigation purposes. Thereupon, the hazard quotient (HQ), and total hazard index (HI) were used to assess the non-carcinogenic risks to different demographic groups. GWQI indicates that groundwater samples are excellent (41.5%), good (40.4%), poor (17%), and very poor (1.1%) classes for drinking purpose. The total hazard index (HI) indicated that 15.2%, 8.5%, 7.4%, and 7.1% of samples express non-carcinogenic health threats to infants, females, children, and males. Irrigation water quality indices (IWQI), namely, EC, sodium adsorption ratio (SAR), residual sodium bicarbonate (RSBC), soluble sodium percent (SSP), permeability index (PI), and magnesium hazard (MH), reveal that 82.2%, 94%, 20.2%, 69.6%, 45.4% and 12.8% of samples have EC < 2250 μS/cm, SAR <26, RSBC <1.25, SSP <60%, PI > 75%, and MH < 50%, respectively, which are suitable for irrigation use. Wilcox diagram shows that 17.54% of total groundwater samples exceed the permissible levels of salt-tolerant crops and solidity hazards in the study area. Furthermore, high concentrations of nitrate (>50 mg/L) and chloride (>1000 mg/L) were detected in the shallow, intermediate, and deep aquifers. GWQI and IWQ maps imply that groundwater in the South-western area is suitable, whereas groundwater in the central area is not recommended for any purpose. These findings provide useful insights into the vulnerable groundwater system of the coastal lowland area of the Mekong Delta related to human activities (agricultural practices, dam construction) and global climate change impacts. Accordingly, appropriate management strategies for water resources and mitigation solutions are imperatively needed to ensure the sustainability of the groundwater resource and the protection of public health in the Mekong Delta.

Spatiotemporal variations in groundwater levels and the impact on land subsidence in CanTho, Vietnam

This study assesses qualitative and quantitative changes in groundwater resources and their impact on land subsidence in Can Tho, Vietnam, from 2000 to 2018. Can Tho city is characterized by scarce water resources and intense industrial, domestic, agricultural, and mining usage, creating water stress. The vertical compaction rates and thus land subsidence, resulting from a head drawdown in three aquifers, were calculated using 1D consolidation of compressible porous media. Experiments were conducted in 16 wells clusters consisting of a total of 48 shallow and deep wells. The three wells from every 16 well clusters from different aquifers, namely the Middle-Upper Pleistocene confined aquifer (qp2-3), the Upper-Pleistocence (qp3), and a well in Holocene (qh), respectively, were examined. The Mann Kendal test with Sen's slope was performed and for most of the wells, negative values of Kendall's tau were found, which indicated decreasing trend of groundwater level. A significant change in groundwater level were also detected during the last eighteen years from 2000 to 2018. The results show significant downward trends of groundwater level for all of the wells of aquifer qp3 and qp2-3 except for a few shallow wells. The trend of this dropdown groundwater level for these deep wells is highly associated with extraction rates. The average subsidence rate of 4.28 cm yr−1 were observed in the study area. Tra Noc Industrial zones (QT8, QT16) showed a high subsidence rate which ranges from 5 to 7 cm yr−1. The calculated subsidence rates indicate the ongoing groundwater overexploitation, which might place Can Tho at risk of increased flooding and saltwater intrusion in the context of climate change and sea-level rise. The findings of this study call for effective policy strategies for sustainable water resource management to limit further land subsidence.

The temporal variations in runoff-generation parameters of the Xinanjiang model due to human activities: A case study in the upper Yangtze River Basin, China

Study regionUpper Yangtze River Basin, China. Study focusThe intensification of climate change and human activities leads to non-stationarity of hydrological processes. Previous studies mainly focus on monthly hydrological or Budyko models. However, it is a challenge that catchment hydrological responses to human activities for daily hydrological models. This study aims to evaluate anthropogenic impacts on water yield of the upper Yangtze River Basin by representing the Xinanjiang model parameters as functions of socio-economic factors. New hydrological insightsThe hydrological parameters WM (soil water storage capacity) and KE (ratio of potential evaporation to pan evaporation) increased in 1976–2000, while the parameter B (non-homogeneity of the soil water storage capacity) declined. It is further demonstrated that the population and the drainage area of reservoirs have the greatest impact on B and WM, respectively. Their linear functional form is validated to be effective for improving streamflow simulation. These findings can help understand the non-stationarity of the rainfall-runoff relationship due to increasing human development and contribute to adaptive development strategies for future water resource management.

MULTIVARIATE STATISTICS APPLIED TO IRRIGATION WATER QUALITY DATA OF A WATERSHED IN THE SEMIARID REGION OF BRAZIL1

ABSTRACT Water scarcity is one of the main problems in the Semiarid region of Brazil, which can be mitigated by water resource management strategies. The objective of this work was to classify waters of a watershed in the Semiarid region of Brazil and select the water attributes that most affect the quality of waters used for irrigation (QWI), using multivariate statistics. The study area was the Riacho da Bica watershed, which is between the municipalities of Portalegre and Viçosa, Rio Grande do Norte, Brazil. The QWI was determined using water samples from 15 collections carried out from 2016 to 2018, in five specific points of the watershed, starting in the spring and following the water course. The water attributes evaluated were: electrical conductivity (EC), potential hydrogen (pH), and sodium (Na+), potassium (K+), magnesium (Mg2+), calcium (Ca2+), carbonate (CO32-), chloride (Cl-), and bicarbonate (HCO3-) contents. The water quality data were subjected to multivariate statistics through factorial analysis (FA) and principal component analysis (PCA). The application of multivariate statistics through FA-PCA generated four principal components. The attributes that most explained the QWI variation were potassium, calcium, and pH for Factor 01, and sodium and RAS for Factor 02. The watershed waters were classified as low risk of salinity and medium risk of sodicity (C1S2) for irrigation purposes.

The effects of climate variability and land-use change on streamflow and nutrient loadings in the Sesan, Sekong, and Srepok (3S) River Basin of the Lower Mekong Basin.

This paper aimed at examining the climate variability and land-use change effects on streamflow and pollutant loadings, namely total suspended sediment (TSS), total nitrogen (T-N), and total phosphorus (T-P), in the Sesan, Sekong, and Srepok (3S) River Basin in the period 1981-2010. The well-calibrated and validated Soil and Water Assessment Tool (SWAT) was used for this purpose. Compared to the reference period, climate variability was found to be responsible to a 1.00% increase in streamflow, 2.91% increase in TSS loading, 11.35% increase in T-N loading, and 19.12% reduction in T-P loading for the whole basin. With regard to the effect of land-use change (LUC), streamflow, TSS, T-N, and T-P loadings increased by 0.01%, 3.70%, 10.12%, and 10.94%, respectively. Therefore, the combination of climate variability and LUC showed amplified increases in streamflow (1.03%), TSS loading (7.09%), and T-N loading (25.05%), and a net effect of decreased T-P loading (10.35%). Regarding the Sekong and Srepok River Basins, the streamflow, TSS, T-N and T-P showed stronger responses to climate variability compared to LUC. In case of the Sesan River Basin, LUC had an effect on water quantity and quality more strongly than the climate variability. In general, the findings of this work play an essential role in providing scientific information to effectively support decision makers in developing sustainable water resources management strategies in the study area.

English

This work aims at characterizing the conditional probability of single or consecutive dry and wet days in West Africa using the first-order Markov chain approach during the monsoon season (June to October). The results show that the probabilities of having a wet day (PW), a wet day preceded by another wet day (PWW) and a wet day preceded by a dry day (PDW) are stronger in regions where the rainfall is maximum (mountain regions). In contrast, the probabilities of having a dry day (PD), a dry day preceded by a wet day (PWD) and a dry day preceded by another dry day (PDD) are lower in the regions with higher precipitation. The seasonal cycle of PWW (PDD) is consistent with that of PW (PD), respectively in Western Sahel and Central Sahel regions. At the interannual timescale, MK test results show that PW and PDW (PD and PDD) exhibit statistically significant increasing (decreasing) trends the Western Sahel and the Central Sahel. Besides, the shorter dry spells (3 days) show statistically significant decreasing trends only in the Western Sahel. The longer dry spells (5, 7 and 10 days) show statistically significant downward trends over the Western and Central Sahel. Wet spells probabilities show non-significant decreasing trends in all sub-domains, except in the Western Sahel for the 10 days spells. Knowledge of theses probabilities will contribute to develop efficient strategies for water resources management and agricultural decision making in West African countries. Key words: Markov chain, rainfall, occurrence, wet spell, dry spell, West Africa.

Attribution of changes in the trend and temporal non-uniformity of extreme precipitation events in Central Asia

Extreme precipitation events exhibit an increasing trend for both the frequency and magnitude on global and regional scales and it has already proven the impact of man-made global warming on the extreme precipitation amplification. Based on the observed datasets and global climate model (GCM) output, this study has evaluated the impact from anthropogenic forcing on the trend and temporal non-uniformity (i.e. increase in unevenness or disparity) of the precipitation amounts (PRCPTOT), extremes (R95p and RX5day) and intensity (SDII) in Central Asia (CA) from 1961 to 2005. Results indicate that radiative forcing changes, mainly driven by human activities, have significantly augmented the extreme precipitation indices in CA. The median trend with the influence of anthropogenic activities for the PRCPTOT, SDII, R95p and RX5day amounted to 2.19 mm/decade, 0.019 mm/decade, 1.39 mm/decade and 0.21 mm/decade during the study period, respectively. A statistically insignificant decrease in non-uniformity was noticed for the PRCPTOT, SDII and RX5day in Central CA (CCA) and Western CA (WCA), while Eastern CA (ECA) was the only region with a statistically significant increase in non-uniformity of the PRCPTOT, SDII, R95p and RX5day by 4.22%, 3.98%, 3.73% and 3.97%, respectively from 1961 to 2005 due to anthropogenic forcing. These results reflect the difference in various regions regarding the impact of anthropogenic forcing on the non-uniformity of extreme precipitation events in CA, which might help to fully understand the role of anthropogenic forcing in the changes of the precipitation extremes in CA and contribute to the development of water resource management strategies.

Uncertainty assessment of water resources and long-term hydropower generation using a large ensemble of future climate projections for the Nam Ngum River in the Mekong Basin

Study regionThe Nam Ngum River Basin, the major tributary of the Mekong River, is located in the Laos PDR. Study focusThis study aims to assess the sensitivity of Nam Ngum 1 reservoir operation to water resource uncertainty driven by a combination of climate change and upstream cascade dam development. New hydrological insights for the regionPrecipitation projections of the basin under a 4° increase scenario vary in the range of −9.6 % to +6.9 %, compared to the historical observed precipitation (present climate). The impact of climate change on hydropower resources was investigated. Based on the combined effect of climate change and upstream cascade dam development, the projected inflow of the Nam Ngum 1 reservoir at the full development stage will change from −16.0 % to +6.5 %, which results in a large range of annual energy production changes from −18.8 % to +2.8 % compared to the current condition (present climate and existing dam stage). Furthermore, water losses from the reservoir due to water discharge from the spillway for extreme floods and evaporation are expected to increase with increasing temperature, which will lead to a loss in energy production. Our study indicates that the operation of hydropower should be adapted to the effects of climate change. This information can be used by stakeholders to propose water resource management strategies.

Design and analysis of statistical probability distribution and non-parametric trend analysis for reference evapotranspiration.

Accurate estimates of reference evapotranspiration are critical for water-resource management strategies such as irrigation scheduling and operation. Therefore, knowledge of events such as spatial and temporal reference evapotranspiration (ETo) and their related principle of statistical probability theory plays a vital role in amplifying sustainable irrigation planning. Spatiotemporal statistical probability distribution and its associated trends have not yet has explored in Pakistan. In this study, we have two objectives: (1) to determine the most appropriate statistical probability distribution that better describes ETo on mean monthly and seasons wise estimates for the design of irrigation system in Khyber Pakhtunkhwa, and (2) to check the trends in ETo on a monthly, seasonal, and annual basis. To check the ETo trends, we used the modified version of the Mann-Kendall and Sen Slope. We used Bayesian Kriging for spatial interpolation and propose a practical approach to the design and study of statistical probability distributions for the irrigation system and water supplies management. Also, the scheme preeminent explains ETo, on a monthly and seasonal basis. The statistical distribution that showed the best fit ETo result occupying 58.33% and 25% performance for the design of irrigation scheme in the entire study region on the monthly level was Johnson SB and Generalized Pareto, respectively. However, according to the Anderson-Darling (AD) and Kolmogorov–Smirnov (KS) goodness of fit measure, seasonal ETo estimates were preferably suited to the Burr, Johnson SB & Generalized Extreme Value. More research work must be conduct to assess the significance of this study to other fields. In conclusion, these findings might be helpful for water resource management and policymaker in future operations.

Sustainable regional water allocation under water-energy nexus: A chance-constrained possibilistic mean-variance multi-objective programming

It is important to manage water resources under water-energy nexus considering both steady economic development and environmental needs. In this study, a water resources management modelling framework of regional water use sectors was established by combining the water resources value theory with the uncertainty theory. The water resources value of different water use sectors was calculated through Cobb-Douglas (C-D) production function and emergy theory to estimate the benefits of water resources accurately. On this basis, a chance-constrained possibilistic mean-variance multi-objective programming (CPMMP) model was established by integrating the classical mean-variance model based on investment portfolio, chance-constrained programming (CCP), possibilistic mean and variance of fuzzy number with multi-objective programming framework. This model can not only deal with the risks of inaccurate water-supply prediction and the fluctuating water supply benefits but also achieve compromise resources consumption, and environmental protection under uncertainty. Taking Shiyang River Basin as an example, the validity of the proposed framework and solution method were verified under different hydrological years, 60%WSB (best water supply benefits) and 90%WSB scenarios. The calculated average water resources value in agricultural, industrial and domestic were 1.92, 109.67 and 20.71 CNY/m3 respectively, and the standard deviation were 0.21, 15.68, 2.60 CNY/m3 respectively. The variability of water resources value in industrial sector were far greater than those in agricultural and domestic sectors. These fluctuations of water resources should be paid attention to in the water resources allocation. The established CPMMP model can effectively reduce the system risks, net carbon emissions and energy consumption under the premise that the system benefits are equivalent to the status quo. Optimal results can provide decision makers energy-saving and emission-reducing water resource management strategies, which are conducive to the sustainable development of the system. Besides, the established framework can also provide a scientific basis and technical support for other resource management in other regions.