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The Water-Food-Energy nexus study identifies developmental challenges and trade-offs present along the transboundary river basins. Intensive reservoir development for hydropower production impacts existing actors in the Lancang-Mekong River Basin. Concerns from these stakeholders highlight three major trade-offs that occur between hydropower and irrigation (HP-AG), hydropower and fisheries (HP-F), and irrigation and fisheries (AG-F). Dam construction has an impact not only on power production but also on ecosystems and ultimately the livelihood of people. In this study, we quantify the effects of reservoir operation on hydropower generation, irrigated crop production and fisheries yield in the Tonle Sap lake through a novel hydro-economic model at the whole basin scale. Our main finding is that trade-offs can be turned into synergetic opportunities. First, the dam operation can increase water availability for irrigation without severely harming hydropower production, raising irrigated crop revenue by 49% and reducing crop losses during droughts by 30%. Second, eco-friendly management increases fisheries yield by up to 75%, but decreases both irrigated crop production (-48%) and power production (-17%). Reservoirs can, therefore, benefit the whole basin by releasing more water in months with high irrigation demand (April and December) and by minimizing the adverse effects of flow fluctuations on the livelihood of farmers and fishers living downstream. Our results also reveal the overlooked trade-off between irrigated agriculture and fisheries. Cross-sectoral and transboundary partnerships should strengthen stakeholder participation in decision-making. Local solutions such as enhanced reservoir operation can respond to the broader global issue of natural resource trade-offs and sharing. Our alternative narrative enhances the dialogue about fair and efficient water use among Mekong riparian countries.

Following the debate on whether drought has become more severe under climate change, this paper assesses drought frequency in northern and eastern India using two datasets of Palmer Drought Severity Index (PDSI) (generated by Dai, 2013 and Sheffield et al., 2012 ). The univariate return period for three drought characteristics (duration, severity and peak intensity) is examined regarding whether drought has occurred with longer duration, higher severity and/or larger peak intensity. The spatial variation of those changes is analyzed through eight areas in the study region. The temporal and spatial comparisons based on the univariate return period show different change patterns of duration, severity and peak intensity in different areas. Generally, in the areas which plant wheat more than rice (areas 1 and 2), drought has been alleviated in duration and intensity after 1955; while in the areas which plant more rice than wheat (areas 3–8), drought have been aggravated in duration, severity and intensity (except for area 8, a coastal area). This spatial change pattern may imply potential crop pattern change, for example, switching from rice to wheat in areas 3–7. Furthermore, the bivariate return period for pairs of drought characteristics based on the copulas and considering correlation between the drought characteristics is examined to understand how bivariate return periods change over time and space. Finally, it is also found that one data set (Sheffield et al.) results in more severe, longer and more intense drought in most of the areas, especially for the drought events with long-return-periods than the other (Dai).

In southern Africa, the connections between climate and the water-energy-food nexus are strong. Physical and socioeconomic exposure to climate is high in many areas and in crucial economic sectors. Spatial interdependence is also high, driven for example, by the regional extent of many climate anomalies and river basins and aquifers that span national boundaries. There is now strong evidence of the effects of individual climate anomalies, but associations between national rainfall and Gross Domestic Product and crop production remain relatively weak. The majority of climate models project decreases in annual precipitation for southern Africa, typically by as much as 20% by the 2080s. Impact models suggest these changes would propagate into reduced water availability and crop yields. Recognition of spatial and sectoral interdependencies should inform policies, institutions and investments for enhancing water, energy and food security. Three key political and economic instruments could be strengthened for this purpose; the Southern African Development Community, the Southern African Power Pool, and trade of agricultural products amounting to significant transfers of embedded water.

South Africa is likely to experience higher temperatures and less rainfall as a result of climate change. Resulting changes in regional water endowments and soil moisture will affect the productivity of cropland, leading to changes in food production and international trade patterns. High population growth elsewhere in Africa and Asia will put further pressure on natural resources and food security in South Africa. Based on four climate change scenarios from two general circulation models (CSIRO and MIROC) and two IPCC SRES emission scenarios (A1B, B1), this study assesses the potential impacts of climate change on global agriculture and explores two alternative adaptation scenarios for South Africa. The analysis uses an updated GTAP-W model, which distinguishes between rainfed and irrigated agriculture and implements water as an explicit factor of production for irrigated agriculture. For South Africa to adapt to the adverse consequences of global climate change, it would require yield improvements of more than 20 percent over baseline investments in agricultural research and development. A doubling of irrigation development, on the other hand, will not be sufficient to reverse adverse impacts from climate change in the country.

Although irrigation in Africa has the potential to boost agricultural productivities by at least 50%, food production on the continent is almost entirely rainfed. The area equipped for irrigation, currently slightly more than 13 million hectares, makes up just 6% of the total cultivated area. More than 70% of Africa’s poor live in rural areas and mostly depend on agriculture for their livelihoods. As a result, agricultural development is key to ending poverty on the continent. Many development organizations have recently proposed to significantly increase investments in irrigation in the region. However, the potential for irrigation investments in Africa is highly dependent upon geographic, hydrologic, agronomic, and economic factors that need to be taken into account when assessing the long-term viability and sustainability of planned projects. This paper analyzes the large, dam-based and small-scale irrigation investment potential in Africa based on agronomic, hydrologic, and economic factors. We find significant profitable irrigation potential for both small-scale and large-scale systems. This type of regional analysis can guide distribution of investment funds across countries and should be a first step prior to in-depth country- and local-level assessment of irrigation potential, which will be important to agricultural and economic development in Africa.

The Yellow River basin is a key food production centre of global importance facing rapidly growing water scarcity. Water availability for agriculture in the basin is threatened by rapid growth in the demand for industrial and urban water, the need to flush sediment from the river's lower reaches, environmental demands and growing water pollution. Climate change is already evident in the basin with long-term declines in river runoff, higher temperatures, and increasing frequency and intensity of drought. The Chinese government has exhausted most options for improving water supply. The challenge will be to switch to improved water demand management, which is hampered by existing governance structures, and lack of integrated agriculture and water resource policies.

Levee setback location and height are important issues in flood levee system design and modification. This paper derives an economic-engineering theory of the optimal trade-off of levee setback for height both for original and redesigned flood levees, demon- strating the interconnection of levee setback, height, costs and risks, and economically optimal design. These analyses assume stationary flood hydrology and static ratios among damageable property value, unit construction cost, and land price. The economic trade-off of levee setback for height depends on economic cost and benefit and hydraulic parameters, and only indirectly on flood frequency and economic damage parameters. The redesign rules derived in this paper indicate conditions where existing levees should be raised or moved in response to changes in conditions. Numerical examples illustrate the results. This paper demonstrates several ideas and theory for economic flood levee system planning and policy rather than providing guidelines for direct design practice.

This study summarizes the concept of the food-energy-water security nexus (FEW nexus). The aim is to create awareness about the importance of the nexus and to enable stakeholders to consider interconnections between the sectors in their work. The FEW nexus is discussed in the context of Africa south of the Sahara (SSA)—using Malawi and Mozambique as case studies. Even though analyzing food, energy, and water security issues simultaneously is critical given the interconnections, summarizing interventions with the FEW nexus approach in Malawi and Mozambique, we found that there are only a limited number of interventions in place. Additionally, this study reviews macro- and microeconomic models that are able to analyze the FEW nexus. On the macrolevel, especially general equilibrium models are discussed, because they show trade-offs and synergies of nexus interventions at all economic levels. These models can help guide policymakers’ understanding of nexus effects ex ante and convince them to think beyond their respective political departments. On the microlevel, the impact of nexus interventions can be assessed with qualitative and quantitative approaches. There are specific challenges for nexus interventions when it comes to aggregation and planning of the targeting. A secondary data analysis of nexus interventions shows that existing data is not sufficient to conduct research specifically related to the FEW nexus. The results of this study will help research programs to reflect the key questions required to enhance adoption of FEW technologies and inform policymakers as they formulate policies that will exploit the strong synergies of food security, energy, and water investments.

"This paper analyzes the effects of climate change on water availability and use in the Limpopo River Basin of Southern Africa, using a linked modeling system consisting of a semi-distributed global hydrological model and the Water Simulation Module (WSM) of the International Model for Policy Analysis of Agricultural Commodities and Trade (IMPACT). Although the WSM simulates all major water use sectors, the focus of this study is to evaluate the implications of climate change on irrigation water supply in the catchments of the Limpopo River Basin within the four riparian countries: Botswana, Mozambique, South Africa, and Zimbabwe. The analysis found that water resources of the Limpopo River Basin are already stressed under today???s climate conditions. Projected water infrastructure and management interventions are expected to improve the situation by 2050 if current climate conditions continue into the future. However, under the climate change scenarios studied here, water supply availability is expected to worsen considerably by 2050. Assessing hydrological impacts of climate change is crucial given that expansion of irrigated areas has been postulated as a key adaptation strategy for Sub-Saharan Africa. Such expansion will need to take into account future changes in water availability in African river basins."

[1] This paper examines levee-protected floodplains and economic aspects of adaptation to increasing long-term flood risk due to urbanization and climate change. The lower American River floodplain in the Sacramento, California, metropolitan area is used as an illustration to explore the course of optimal floodplain protection decisions over long periods. A dynamic programming model is developed and suggests economically desirable adaptations for floodplain levee systems given simultaneous changes in flood climate and urban land values. Economic engineering optimization analyses of several climate change and urbanization scenarios are made. Sensitivity analyses consider assumptions about future values of floodplain land and damageable property along with the discount rate. Methodological insights and policy lessons are drawn from modeling results, reflecting the joint effects and relationships that climate, economic costs, and regional economic growth can have on floodplain levee planning decisions.

Levee setback (location) and height are important issues in flood levee system design or modification. This paper derives an economic-engineering theory of the optimal trade-off of levee setback for height for both original and re-designed flood levees, demonstrating the interconnection of levee setback, height, costs and risks, and economically optimal decisions. All the analyses assume that hydrologic and economic conditions are “static”. Expected total flood control costs are shown to be convex for conditions of wide channels where flood flows have a lognormal frequency distribution. The re-design rules derived in this paper hold for much wider conditions. Numerical examples illustrate the results. This paper demonstrates several ideas and theory for economic flood levee system planning and policy rather than providing guidelines for direct design practice.

Long-term hydrologic forecasts are not widely used in water resource decision-making practices, partially due to the large forecast uncertainty involved. This paper formulates how long-term (annual) hydrologic forecasts might improve the management decisions of an integrated regional water resources system, using a three-stage stochastic optimization model. The three stage model is developed based on a two-stage model, which the paper also examines analytically. Both models incorporate decisions regarding crop mix, irrigation technology, conjunctive surface and ground water operation, urban water conservation, and water transfers between the agricultural and urban areas. The first stage includes all permanent decisions, such as acreage of perennial crops and urban conservation measures that will exist for multiple years. The second stage consists of temporary decisions, like acreage of annual crops, annual urban conservation measures and annual water transfers, whose impacts are limited within a year, based on imperfect forecast information. The third stage of the three-stage model comprises recourse decisions that “adjust” the temporary decisions in the second stage based on the “realizations” of hydrology which are conditional on each of the year type forecast employed in the second stage.