Surface Water Availability Research Articles

Spatial and Temporal Changes in Surface Water Area of Sri Lanka over a 30-Year Period

Sri Lanka contains a large number of natural and man-made water bodies, which play an essential role in irrigation and domestic use. The island has recently been identified as a global hotspot of climate change extremes. However, the extent, spatial distribution, and the impact of climate and anthropogenic activities on these water bodies have remained unknown. We investigated the distribution, spatial and temporal changes, and the impacts of climatic and anthropogenic drivers on water dynamics in Dry, Intermediate, and Wet zones of the island. We used Landsat 5 and Landsat 8 images to generate per-pixel seasonal and annual water occurrence frequency maps for the period of 1988–2019. The results of the study demonstrated high inter- and intra-annual variations in water with a rapid increase. Further, results showed strong zonal differences in water dynamics, with most dramatic variations in the Dry zone. Our results revealed that 1607.73 km2 of the land area of the island is covered by water bodies, among this 882.01 km2 (54.86%) is permanent and 725.72 km2 (45.14%) is seasonal water area. Total inland seasonal water increased with a dramatic annual growth rate of 7.06 ± 1.97 km2 compared to that of permanent water (4.47 ± 2.08 km2/year). Sri Lanka has the highest permanent water area during December–February (1045.97 km2), and drops to the lowest in May–September (761.92 km2) when the seasonal water (846.46 km2) is higher than permanent water. The surface water area was positively related to both precipitation and Gross Domestic Product, while negatively related to the temperature. Findings of our study provide important insights into possible spatiotemporal changes in surface water availability in Sri Lanka under certain climate change and anthropogenic activities.

Assessment of Water Supply and Demand in the Lower Mahi Sub-basin using WEAP Model

This study deals with the future water demand assessment in Lower Mahi Sub-basin, Bihar, India using Water Evaluation and Planning Model (WEAP). The river Mahi is flowing through the Mahi sub-basin, which is a tributary to the Ganga river. Understanding and analyzing the past and present water supply and demand scenarios and prediction of future scenarios are indispensable for this area. In the WEAP model development phase, two scenarios are considered: past scenario (2004-2013), present and future scenarios (2016-2021) together. The water supply nodes used are Mahi river, groundwater and canals from Gandak river. The results from the trend of supply and demand shows that the sub-basin is water deficit for most part of year except during July to September. The water deficit is also observed during Rabi season when there is no rainfall or availability of surface water is nil for the crops, especially wheat. This results in more and more usage of groundwater and hence leads to groundwater depletion. By analyzing the results of the WEAP Model for the present and future scenario, a depletion in groundwater storage at a faster rate is observed with the existing climatic conditions and increased population, livestock and industry.

Appraisal of Climate Change and Its Impact on Water Resources of Pakistan: A Case Study of Mangla Watershed

Water resources are highly dependent on climatic variations. The quantification of climate change impacts on surface water availability is critical for agriculture production and flood management. The current study focuses on the projected streamflow variations in the transboundary Mangla Dam watershed. Precipitation and temperature changes combined with future water assessment in the watershed are projected by applying multiple downscaling techniques for three periods (2021–2039, 2040–2069, and 2070–2099). Streamflows are simulated by using the Soil and Water Assessment Tool (SWAT) for the outputs of five global circulation models (GCMs) and their ensembles under two representative concentration pathways (RCPs). Spatial and temporal changes in defined future flow indexes, such as base streamflow, average flow, and high streamflow have been investigated in this study. Results depicted an overall increase in average annual flows under RCP 4.5 and RCP 8.5 up until 2099. The maximum values of low flow, median flow, and high flows under RCP 4.5 were found to be 55.96 m3/s, 856.94 m3/s, and 7506.2 m3/s and under RCP 8.5, 63.29 m3/s, 945.26 m3/s, 7569.8 m3/s, respectively, for these ensembles GCMs till 2099. Under RCP 4.5, the maximum increases in maximum temperature (Tmax), minimum temperature (Tmin), precipitation (Pr), and average annual streamflow were estimated as 5.3 °C, 2.0 °C, 128.4%, and 155.52%, respectively, up until 2099. In the case of RCP 8.5, the maximum increase in these hydro-metrological variables was up to 8.9 °C, 8.2 °C, 180.3%, and 181.56%, respectively, up until 2099. The increases in Tmax, Tmin, and Pr using ensemble GCMs under RCP 4.5 were found to be 1.95 °C, 1.68 °C and 93.28% (2021–2039), 1.84 °C, 1.34 °C, and 75.88%(2040–2069), 1.57 °C, 1.27 °C and 72.7% (2070–2099), respectively. Under RCP 8.5, the projected increases in Tmax, Tmin, and Pr using ensemble GCMs were found as 2.26 °C, 2.23 °C and 78.65% (2021–2039), 2.73 °C, 2.53 °C, and 83.79% (2040–2069), 2.80 °C, 2.63 °C and 67.89% (2070–2099), respectively. Three seasons (spring, winter, and autumn) showed a remarkable increase in streamflow, while the summer season showed a decrease in inflows. Based on modeling results, it is expected that the Mangla Watershed will experience more frequent extreme flow events in the future, due to climate change. These results indicate that the study of climate change’s impact on the water resources under a suitable downscaling technique is imperative for proper planning and management of the water resources.

An interdisciplinary framework for using archaeology, history and collective action to enhance India’s agricultural resilience and sustainability

South Asia has a deep history of agriculture that includes a range of past farming systems in different climatic zones. Many of these farming systems were resilient to changes in climate and sustainable over long periods of time. India’s present agricultural systems are facing serious challenges, as they have become increasingly reliant on the unsustainable extraction of groundwater for irrigation. This paper outlines an interdisciplinary framework for drawing on patterns from the past to guide interventions in the present. It compares past and present strategies for water management and use in semi-arid and temperate Punjab with equatorial Telangana. Structural differences in water use in these two regions suggest that a range of interventions should be adopted to expand the overall availability of surface water for agricultural systems in India, in combination with empowering local communities to create their own water management rules. Active interventions focus on the efficient use of water supplies, and increasing surface water availability through renovation of collective ponds and reservoirs. We argue that this conceptual framework has significant potential for guiding agronomic and economic interventions in the future.

Incorporating hydrology into climate suitability models changes projections of malaria transmission in Africa

Continental-scale models of malaria climate suitability typically couple well-established temperature-response models with basic estimates of vector habitat availability using rainfall as a proxy. Here we show that across continental Africa, the estimated geographic range of climatic suitability for malaria transmission is more sensitive to the precipitation threshold than the thermal response curve applied. To address this problem we use downscaled daily climate predictions from seven GCMs to run a continental-scale hydrological model for a process-based representation of mosquito breeding habitat availability. A more complex pattern of malaria suitability emerges as water is routed through drainage networks and river corridors serve as year-round transmission foci. The estimated hydro-climatically suitable area for stable malaria transmission is smaller than previous models suggest and shows only a very small increase in state-of-the-art future climate scenarios. However, bigger geographical shifts are observed than with most rainfall threshold models and the pattern of that shift is very different when using a hydrological model to estimate surface water availability for vector breeding.

Wetland habitat stability assessment in hydro-geomorphological (HGM) and surface water availability (SWA) conditions in a lower Gangetic floodplain region of Eastern India

Floodplain wetlands in their optimum habitat condition act as the preventive mechanism from environmental degradation like pollution, lowering of groundwater table, flood, temperature control and others. Therefore, the protection and stability condition assessment of these wetlands are very much indispensable for the sake of the environment. In the present work, the habitat stability assessment of the wetlands of a floodplain region produced by River Ganga has been done considering the hydro-geomorphological (HGM) and surface water availability (SWA) parameters. The fuzzy classification (FC) and composite indexing (CI) method have been applied to perform the analysis. The result suggests that 16%–24% of wetland area is very highly prone to loss and 33%–36% area needs proper management whereas only 9%–11% wetlands are very highly stable. The wetlands have shown a rise in the average seasonal water level fluctuation from 2.18 m in 2014 to 3.38 m in 2018 which indicates more drying out condition during lean months. From morphogenetic perspective, nearly 43% of wetlands are riverine and in terms of HGM classification 77% of the wetlands are groundwater depressions (GWD). So, lack of water supply all throughout the year, seasonal water level fluctuation and absence of active river-wetland links are mainly responsible for the degradation of habitat stability condition of the wetlands. The results have been validated over different ground locations using kappa index and ROC curve method. It suggests that both these methods are very much accurate and between these two, FC method has given better result.

Satellite monitoring of surface water variability in the drought prone Western Cape, South Africa

Surface water plays a fundamental role in supporting life and the functioning of various ecosystems. In this regard, its availability and variability influence the functioning of various ecosystems and most importantly human livelihoods. This becomes critical in drought prone and water-scarce areas of sub-Saharan Africa. The use of satellite remote sensing is increasingly becoming the primary data source for water resources monitoring. However, with emerging and advances in satellite remote sensing data, their ability in monitoring water resources remains uncertain. In addition, the remote sensing of surface water mapping has been limited to specific periods, which undermines the influence of seasonality on their spatial variability. This study therefore assessed the potential of Landsat-8 Operational Land Imager and Sentinel-2 Multi-Spectral Instrument derived Normalised Difference Water Index (NDWI), Modified Normalised Difference Water Index Land Surface Water Index (LSWI+5) and Modified Normalised Difference Index (MNDVI), for monitoring seasonal surface waterbodies in the Western Cape, South Africa. The derived remote sensing estimates were assessed using the Producers', User's, Overall accuracies as well the Kappa coefficient. The spatial variations were also linked to monthly evapotranspiration, rainfall and temperature. These climatic factors all contribute to seasonal surface water availability. Further, the satellite-derived estimates were compared using the analysis of variance (ANOVA), to test whether there were any significant differences (α = 0.05) in their and mapping detection abilities. The results indicated that both sensors managed to detect and map surface water variations and it was observed that surface waterbodies varied spatially over time. During the wet season, more surface waterbodies were detected than during the dry season. The majority of waterbodies were detected by both sensors. Most of these waterbodies were found in the south western part of the study area and all the indices showed similar sizes and presence of seasonal surface waterbodies. Normalised Difference Water Index (NDWI) performed the best and yielded the highest accuracy, however, the Land Surface Water Index VI (LSWI+5) results overestimated the size and occurrence of surface waterbodies, when compared to other indices, especially during the wet season. The derived waterbodies followed a similar pattern with the observed climate data and evapotranspiration rates during the study period. Landsat 8 derived Normalised Difference Water Index (NDWI) performed slightly better when compared to other indices, with 92.33% and a Kappa coefficient of 84.67% in detecting and mapping surface waterbodies. On the other hand, Sentinel-2 produced lower classification estimates. Statistical analysis results demonstrated significant differences (α = 0.05) in the detection and mapping ability of different satellite-derived indices. Overall, this work demonstrates the potential of using Landsat 8 and Sentinel 2 data in understanding spatial variations in surface water.

Past (1971–2018) and future (2021–2100) pan evaporation rates in the Czech Republic

Evaporation from open water surfaces is often estimated based on the pan evaporation (Epan), which is an essential measure for estimating atmospheric evaporative demand. Within the Central European region, Epan appears to be slightly underestimated in the case of the hydrological balance of water bodies. In the context of the recent multi-year period of drought, significant losses of surface water deposits were observed in countries of Central Europe. In spite of the ‘evaporation paradox’ phenomenon, Epan is not generally decreasing as expected by many studies from past decades. Recorded observations from the Czech Republic show an increase in Epan, which is associated with an increase in global radiation and vapor pressure deficit. The vast majority of meteorological stations show a strong or very strong increase in Epan during April, June, July and August. During the 1971–2018 period, the annual mean Epan has been increasing by an average of 2.97 mm yr−1. For the period 2001–2018, the mean Epan was 18% higher (519 mm) than the 1971–2000 average (440 mm). Our simulations of future scenarios, using regional climate models, predicted a growth in Epan of up to 27–54%. Such an increase in evaporation would cause serious consequences for surface water availability and agricultural production during the periods of drought in the Czech Republic, as the drought period 2014–2018 has clearly demonstrated.

Use of multi-temporal satellite data for monitoring pool surface areas occurring in non-perennial rivers in semi-arid environments of the Western Cape, South Africa

Hydrological monitoring networks do not adequately cover non-perennial rivers in most parts of Africa partly because river flows do not frequently occur on these rivers. However, in the arid and semi-arid regions flows occurring on these rivers are an important resource that have to be managed judiciously. The lack of data on magnitudes, timing and frequency of non-perennial river flows constrain sustainable management of their water resources. The availability of moderate resolution satellite data (e.g. Sentinel-2 Multispectral Instrument and Landsat 8 Operational Land Imager) offers an opportunity to monitor the surface water availability specifically changes in surface areas covered with water in pools along these rivers. In this study, we investigated the use of remote sensing data to detect and monitor changes of water surface areas of pools along three non-perennial rivers and one perennial river in the Western Cape, South Africa, from 2016 to 2017, using Landsat 8 and Sentinel-2 datasets. We assessed a range of image pre-processing and image classification techniques to determine the most suitable method for surface water identification and pool area estimation along the selected rivers. The following indices were used; Normalised Difference Water Index (NDWI), Modified NDWI (MNDWI), Normalised Difference Vegetation Index (NDVI), Automated Water Extraction Index for shadowed (AWEIsh), non-shadowed regions (AWEInsh), and the Multi-Band Water Index (MBWI). The NDWI computed from Sentinel-2 TOA reflectance datasets was found to be the most suitable index for mapping pools, with an overall accuracy ranging between 60 and 86%. This index was used successfully to establish the variations of surface areas of pools covered with water along the Breede, Nuwejaars, Tankwa and Touws Rivers during the 2016–2017 period. The temporal variations of pool areas could be explained as expected by changes of rainfall and potential evapotranspiration. Overall, the study demonstrated the feasibility of using moderate resolution datasets to monitor pool changes of areas covered with water in non-perennial rivers, which contributes to improved management of water resources particularly in arid and semi-arid environments.

Divergent effects of climate change on future groundwater availability in key mid-latitude aquifers

Groundwater provides critical freshwater supply, particularly in dry regions where surface water availability is limited. Climate change impacts on GWS (groundwater storage) could affect the sustainability of freshwater resources. Here, we used a fully-coupled climate model to investigate GWS changes over seven critical aquifers identified as significantly distressed by satellite observations. We assessed the potential climate-driven impacts on GWS changes throughout the 21st century under the business-as-usual scenario (RCP8.5). Results show that the climate-driven impacts on GWS changes do not necessarily reflect the long-term trend in precipitation; instead, the trend may result from enhancement of evapotranspiration, and reduction in snowmelt, which collectively lead to divergent responses of GWS changes across different aquifers. Finally, we compare the climate-driven and anthropogenic pumping impacts. The reduction in GWS is mainly due to the combined impacts of over-pumping and climate effects; however, the contribution of pumping could easily far exceed the natural replenishment.

Sustainable management of a cropping system under salt stress conditions (Korba, Cap-Bon, Tunisia).

Korba is a coastal region and the main production area for strawberries, tomatoes, and peppers in Tunisia. Due to the use of saline groundwater in irrigation, soil salinization increases in the area. Farmers are therefore forced to reduce the salinity in the soil by adopting a suitable water management strategy "blended water," with the appropriate irrigation system "drip irrigation," and new farming techniques "crop combinations and crop rotations" to achieve sustainability. Based on the electrical conductivity (EC) of the groundwater (5.05dS/m) and freshwater (1.7dS/m), in our pilot plot, we determine that the blended water used in irrigation must contain 28.55% of groundwater with 71.45% freshwater to have a 50%strawberry yield potential because strawberry is the most salt-sensitive crop produced in the region. The strawberry-pepper's combination is a way to improve farmers' incomes with a 200% intensification rate, taking advantage of the rains and the availability of surface water during the wet season. However, the soil salinity used to increase under these crops from 1.28 dS/m in November 2018 to 3.04 dS/m of soil EC in September 2019. This is beyond the strawberry salt tolerance threshold (1 dS/m). Even after planting summer crops, tomatoes, and peppers, the rate of evolution of soil salinity exceeds 200% (~ 4.5dS/m) and 122% (~ 3dS/m), respectively. Therefore, the rotation becomes necessary to reduce the soil salinity and thus prepare the soil for the next planting of tomatoes, peppers, and strawberry-pepper's combination. The introduction of rainfed crops or fallow in the agricultural rotation system helped farmers to reduce soil salinity with about 56% and 67.2% for crop rotations including summer crops and the strawberry-pepper's combination, respectively, with a return period of 1year.

From Satellite to Supply Chain: New Approaches Connect Earth Observation to Economic Decisions

Global supply chains shift environmental and social impacts of consumption to remote locations. This opacity challenges many sustainability goals. To help businesses and governments realize more sustainable supply chains, new approaches are using spatial data and machine-learning techniques to connect Earth observation data to conventional economic tools.

Contiguous U.S. surface water availability and short-term trends of wastewater effluent flows in San Antonio, TX

Surface water is a vital and sometimes stressed resource in the U.S. The quantity of this resource is threatened by population shifts and growth concurrently with climate change intensification. Additionally, growing population centers can impact water quality by discharging treated wastewater effluent, which is typically of lower quality than its receiving surface waters. Depending on baseflow and environmental factors, this could decrease water quality. From a previous model prepared in our lab, this study can improve the understanding of water resource quality and quantity, surface water availability for the contiguous U.S. was estimated for each USGS Hydrologic Unit Code (HUC) during 2015. The Mississippi River generally served as a dividing line for surface water availability, with five of the six regions with very low water availability (<24,000 LD−1Km−2) residing in the west. These same areas also experience more drought as well as more severe droughts than regions in the east. In regions with lower surface water flows, their water quality is more susceptible to the influence of wastewater effluent discharges, especially near large and growing population centers like San Antonio, Texas. A prediction model was established for this city, which found that from 2009 to 2017 wastewater effluent increased by 1.8%. As cities grow, especially in the Southwest and Western U.S. together with intensified climate change, surface water quantity and quality become more crucial to sustainability. This study shows where surface water availability is already an issue and provides a model to estimate, as well as project, wastewater effluent flows into surface water bodies.

Bacterial surface motility is modulated by colony-scale flow and granular jamming

Microbes routinely face the challenge of acquiring territory and resources on wet surfaces. Cells move in large groups inside thin, surface-bound water layers, often achieving speeds of 30 µm s-1 within this environment, where viscous forces dominate over inertial forces (low Reynolds number). The canonical Gram-positive bacterium Bacillus subtilis is a model organism for the study of collective migration over surfaces with groups exhibiting motility on length-scales three orders of magnitude larger than themselves within a few doubling times. Genetic and chemical studies clearly show that the secretion of endogenous surfactants and availability of free surface water are required for this fast group motility. Here, we show that: (i) water availability is a sensitive control parameter modulating an abiotic jamming-like transition that determines whether the group remains fluidized and therefore collectively motile, (ii) groups self-organize into discrete layers as they travel, (iii) group motility does not require proliferation, rather groups are pulled from the front, and (iv) flow within expanding groups is capable of moving material from the parent colony into the expanding tip of a cellular dendrite with implications for expansion into regions of varying nutrient content. Together, these findings illuminate the physical structure of surface-motile groups and demonstrate that physical properties, like cellular packing fraction and flow, regulate motion from the scale of individual cells up to length scales of centimetres.

Modeling permafrost distribution over the river basins of Mongolia using remote sensing and analytical approaches

The spatial distribution of permafrost and associated mean annual ground temperature (MAGT) and active layer thickness (ALT) are crucial data for hydrological studies. In this paper, we present the current state of knowledge on the spatial distribution of the permafrost properties of 29 river basins in Mongolia. The MAGT and ALT values are estimated by applying TTOP and Kudryavtsev methods. The main input of both methods is the spatially distributed surface temperature. We used the 8-day land surface temperature (LST) data from the day- and night-time Aqua and Terra images of the moderate resolution imaging spectroradiometer (MODIS). The gaps of the MODIS LST data were filled by spatial interpolation. Next, an LST model was developed based on 34 observational borehole data using a panel regression analysis (Baltagi, Econometric analysis of panel data, 3 edn, Wiley, New York, 2005). The model was applied for the whole country and covered the period from August 2012 to August 2013. The results show that the permafrost covers 26.3% of the country. The average MAGT and ALT for the permafrost region is − 1.6 °C and 3.1 m, respectively. The MAGT above -2 °C (warm permafrost) covers approximately 67% of the total permafrost area. The permafrost area and distribution in cold and warm permafrost varies highly over the country, in particular in regions where the river network is highly developed. High surface temperatures associated with climate change would result in changes of permafrost conditions, and, thus, would impact the surface water availability in these regions. The data on permafrost conditions presented in this paper can be used for further research on changes in the hydrological conditions of Mongolia.

Mitigation Ponds Offer Drought Resiliency for Western Spadefoot (Spea hammondii) Populations

Synergistic effects of habitat loss, drought, and climate change exacerbate amphibian declines. In southern California urbanization continues to convert natural habitat, while prolonged drought reduces surface water availability. Protection of biodiversity may be provided through mitigation; however, the long-term effectiveness of different strategies is often unreported. As a mitigation measure for building a new development within occupied Spea hammondii (western spadefoot) habitat in Orange County, California, artificial breeding pools were constructed at two off-site locations. Spea hammondii tadpoles were translocated from the pools at the development site to two off-site locations in 2005–2006. We conducted surveys a decade later (2016) to determine if S. hammondii were persisting and breeding successfully at either the original development site or the human-made pools at the two mitigation sites. We also verified hydroperiods of any existing pools at all three locations to see if any held water long enough for successful S. hammondii recruitment through metamorphosis.During our study, no pooling water was detected at two of three main sites surveyed, and no S. hammondii were observed at these locations. Twelve of the 14 pools created at only one of the two mitigation sites held water for over 30 d, and we detected successful breeding at seven of these pools. Recruitment in some mitigation ponds indicated that S. hammondii habitat can be created and maintained over 10+ yr, even during the fifth year of a catastrophic drought. Therefore, this may also serve as a conservation strategy to mitigate climate change and habitat loss.

“Submerges … Coming out Again and Then Flowing”: What Historical Documents Tell Us About the Character of the Santa Cruz River

The Santa Cruz River, like all the major rivers in southeastern Arizona and the region, had a permanent year-round flow that was restricted to limited segments of the river. This is where the Sobaipuri O’odham established their villages because the reliable surface flow allowed them to farm with irrigation canals. Early historical period observations indicate that the Santa Cruz and other regional rivers were characterized by patchworks of pasturelands, agricultural fields and canals, shady groves of mature trees, marshes, and expanses of dry sand, in contrast to the many previously suggested reconstructions. The underlying fundamentals of the river valley have been determined by surface water availability and although periodically transformed by floods, downcutting, drought, and human factors the riparian corridor has regenerated.

Late Pleistocene lake level history of Lake Mungo, Australia

Lake Mungo is a currently dry lake basin in the semi-arid zone of southeastern Australia. The transverse dune system on the downwind side contains a record of human occupation of international importance. It also contains one of the most continuous records of climate change over the last glacial cycle in the Australia desert. In this paper we provide a framework for the interpretation of lake level history from before the arrival of people (>41 ka) until after the establishment of the pastoral industry in the area. We present 83 optically stimulated luminescence ages from the Lake Mungo lunette. The lake level history is reconstructed from 34 stratigraphic sections along three transects through the lunette. The dating reveals considerable lake level fluctuations through time which occur over a depth range of ∼10 m in the basin. At its height, probably at multiple times before 20 ka, the lake held more than 1 km3 of water and at its final level at ∼19 ka, contained only 0.03 km3. The inception of Lake Mungo appears to have taken place during the mid-Pleistocene between ∼256 and 369 ka. During the last glacial cycle, Lake Mungo was almost continuously wetter than present from shortly after 60 ka until ∼19 ka. The Upper Mungo, Arumpo and Zanci units represent a succession of lake filling and drying events, briefly interspersed by soils. The final Zanci unit does not represent a single high lake phase, but an initial lake filling followed by a series of short-lived lake level events within a brief period of a few thousand years. At the conclusion of this event, the lake remained dry until the present day. Four OSL ages from a linear dune upwind of Lake Mungo indicates regional aeolian activity from ∼30 ka until present. Widespread erosion that produces the characteristic topography of the lunette began after the arrival of British pastoralists and traditional aboriginal ways of life overlapped briefly with this erosion. The presence of water in Lake Mungo closely corresponds to periods when regional surface temperature was colder than present during the late Pleistocene. Our new data supports a model that decreased evaporation and increased runoff were primarily responsible for increased availability of surface water in the hydrological cycle.

The Benefit of Using an Ensemble of Global Hydrological Models in Surface Water Availability for Irrigation Area Planning

Hydrological data and information on the availability of water are essential to support water allocation decisions in irrigated agriculture, especially under increasingly water scarce conditions. However, in many agricultural regions hydrological information is scarce, leading to sub-optimal water allocation decisions and crop yield reduction. Here we assess the benefit of using surface water availability estimates derived from an ensemble of global hydrological models for establishing the potential area that can be irrigated; where the size is determined based on agreed water supply reliability targets. Risky outcomes of the annual agricultural production due to the true occurrence of water scarcity are generated for both the reference and established irrigation areas, resulting in a Relative Utility Value (RUV) that expresses the utility of the information used. Results show that using an ensemble of global hydrological models provides more robust estimates of the planned area compared to using any of the single global models that constitutes the ensemble. A comparison of the information content in the ensemble shows that an ensemble with a period of record of 15 years has an information content equivalent to a single model of 30 years.

Towards sustainable water management in an arid agricultural region: A multi-level multi-objective stochastic approach

Water-shortage crisis is threatening the food production and sustainable development around the world. Especially for arid agricultural regions, it is necessary to plan sustainable agricultural water management strategies for improving water use efficiency. But there are many complexities in it, such as multiple decision-making levels, objectives, water users and uncertainties. To effectively tackle these complexities, this study presents a novel optimization-modeling approach consisting of a multi-level multi-objective stochastic programming (MLMOSP) model and weighting quantification method for formulating sustainable water-allocation schemes in arid agricultural regions. The MLMOSP model incorporates multi-level programming, multi-objective programming, and stochastic expectation programming into a general framework. The proposed approach is capable of: 1) quantifying key factors affecting water-allocation systems through weighting quantification methods; 2) describing the main conflicting objectives of each decision-making level, including economic benefits, environment impacts, fairness, effectiveness, and crop yield; 3) considering tradeoffs among conflicting objectives, and 4) reflecting the leader-follower relationship under different scenarios of surface water availability at a regional scale and a monthly temporal resolution. The proposed approach is applied to a real-world case in a typical arid agricultural region of northwest China for verifying its validity. From this real-world case, it is found that: 1) optimization results corresponding to different flow-level scenarios of surface runoff can provide upper-, middle-, and lower-level decision makers with a set of decision alternatives to help identify the most appropriate management strategy; and 2) multiple model comparisons show that the MLMOSP approach can not only give more practical results guaranteeing the achievement of decision-making goals at different decision-making levels, but also help reduce groundwater extraction under different flow level scenarios of surface runoff.