An Analysis of Sector-Based Water Supply and Demand

This chapter sought to assess sector-based current water use levels in Sanyati catchment, assess a possibility of new ways of managing the catchment water using inter-basin transfer systems, and assess future water demands projection using WEAP model. The study was both quantitative and qualitative in nature. Interviews and observations were the main primary data collection instruments. Findings showed that the main sectors and institutions that utilised water in the catchment were mining, agriculture, manufacturing industry, and local authorities. Local authorities and farming sectors were the major users of water. WEAP model results showed a steady increase in demand for water as a result of both population growth and agricultural activities water demand. The study mapped possible inter-basin transfer routes and recommends water harvesting as part of development and management in Sanyati catchment to address the problem of water shortage.

Avaliação de contribuição do reservatório de Movene na bacia hidrográfica do rio Umbeluzi em Moçambique

A gestão dos recursos hídricos na bacia hidrográfica do rio Umbeluzi é uma questão fundamental devido ao agravamento de escassez de água nos centros urbanos e na agricultura que pode pôr em causa os valores socioculturais, ecológicos e econômicos. Torna-se ainda mais importante o fato de ser uma bacia internacional, cuja demanda por água tem aumentando em função de expansão agrícola e crescimento populacional. O estudo avaliou a contribuição do novo reservatório de Movene e novas regras de prioridade na alocação de água superficial para atender às diferentes necessidades usando o modelo WaterEvaluation and Planning System – WEAP. O modelo foi validado no período 2005-2011 apresentando o NSE de 0,69 e Bias de 5,2% no volume do reservatório e 2005 com NSE de 6,7 e Bias de 6,0% na vazão. Os resultados mostram menor contribuição do reservatório de Movene, a demanda não atendida no abastecimento doméstico passou de 33,6 hm3 para 10,1 hm3 no cenário de Referência e de 57,3 hm3 para 19,9 hm3 no cenário Maior Crescimento em 2040. Considerando o mesmo ano, a demanda não atendida na agricultura caiu de 12,9 hm3 para 4,1 hm3 e de 22 hm3 para 10,3 hm3 nos cenários de Referência e de Maior Crescimento. No sector industrial apenas o cenário Maior Crescimento apresenta demanda não atendida, tendo saído de 7,4 hm3 para 0,3 hm3 em 2040. Esses resultados enfatizam a necessidade de implementação de estratégias de gestão de lado de demanda para minimizar os impactos de escassez de água. Contribution assessment of the Movene reservoir in the Umbeluzi river basin in Mozambique A B S T R A C TThe management of water resources in the Umbeluzi River basin is an important issue due to the worsening of water scarcity in urban centres and in agriculture, which can jeopardize socio-cultural, ecological and economic values. Even more important is the fact that it is an international basin, whose demand for water has been increasing due to agricultural expansion and population growth. The study evaluated the contribution of the new Movene reservoir and new rules of priority in the allocation of surface water to meet different needs usingWater Evaluation And Planning (WEAP) model. WEAP modelwas validated from 2005 to 2011 with NSE of 0.69 and Bias of 5.2% in the volume of the reservoir and 2005 with an NSE of 6.7 and Bias of 6.0% in the flow. The results demonstrate a lower contribution of the Movene reservoir, the unmet demand in domestic supply went from 33.6 hm3to 10.1 hm3 in the Reference scenario and from 57.3 hm3to 19.9 hm3 in the Reference scenario Higher Growth scenario in 2040. Considering the same year, unmet demand in agriculture fell from 12.9 hm3to 4.1 hm3 and from 22 hm3to 10.3 hm3 in the Reference and Higher Growth scenarios. In the industrial sector, only the Highest Growth scenario has unmet demand, having gone from 7.4 hm3to 0.3 hm3 in 2040. These results emphasize the need to implement demand-side management strategies to minimize the impacts of water scarcity.Keywords: water resources, water demand, Umbeluziriver, WEAP model.

ALANA RIVER BASIN MANAGEMENT

The main aim of this study is to highlight how the Alana River Basin (ARB) will meet future water needs and optimal monthly water distribution policies. The Water Evaluation and Planning System (WEAP) model was applied in order to determine the ARB and the operation plan policy using data for the past 16 years (2000-2015). The model result determined that the current regulations and practices regarding water use and pollution patterns are inadequate. An ideal scheme has been developed and implemented for various scenarios such as domestic water needs, irrigation water, and tourism. Four scenarios have been considered in this study, which are basic scenarios, a higher population growth scenario, a severe flow requirements scenario, and a scenario of adding dams. Comparisons show that the demand for water from April to September is high due to the agriculture season and the high temperature. The maximum demand for water is 3 million cubic meters, which occurs in August, while the proposed dam provides only 2 million cubic meters. In addition, the maximum demand for domestic water is 0.4733 MCM and the minimum is 0.36978 MCM, which is roughly the same level of water demand for every month. Accordingly, the government should start supplementing the Gali Bale dam. However, it is not a sufficient dam to cover the water demand, so the construction of additional dams is strongly suggested.

River Water Quality and Quantity Determinants in a Developing Country

Developing countries rely to a large extent on international donors to improve water security. Yet, international interventions often end up with low efficiency impacts because of the lack of a priori comprehensive projections. With this in mind, this paper presents a scenario-based methodology to forecast river water quantity and quality in a common multi-stressor situation, that is combined impact of climate change, population growth and wastewater discharge. As an illustrative case, El Kalb River basin, in Lebanon, was simulated under four scenarios up to year 2050, using Water Evaluation and Planning (WEAP) model. The observed trends indicate that mean annual streamflow and flow to groundwater could decrease by around 10 to 23% each due to climate change, while water demand is expected to increase by 16 to 32%. As to water quality, the maximum BOD of 68 mg/L (in 2019) can be decreased by introducing wastewater treatment (starting 2021 as planned by national authorities) to 44 mg/L, only to increase again to 63 mg/L in 2050 due to population growth. Considering climate change, water quality is expected to deteriorate further and the maximum BOD would reach 118 mg/L and 147 mg/L in 2050 under RCP 4.5 and RCP 8.5 scenarios, respectively. Even though the planned wastewater treatment facilities would reduce BOD by 34%, it was shown that the river would never meet water standards – under any of the proposed scenarios. The approach adopted in this paper is recommended for quantification of the efficiency of river protection plans in developing areas.

Integrated Operation of Multi-Reservoir and Many-Objective System Using Fuzzified Hedging Rule and Strength Pareto Evolutionary Optimization Algorithm (SPEA2)

In this paper, a many-objective optimization algorithm was developed using SPEA2 for a system of four reservoirs in the Karun basin, including hydropower, municipal and industrial, agricultural, and environmental objectives. For this purpose, using 53 years of available data, hedging rules were developed in two modes: with and without applying fuzzy logic. SPEA2 was used to optimize hedging coefficients using the first 43 years of data and the last 10 years of data were used to test the optimized rule curves. The results were compared with those of non-hedging methods, including the standard operating procedures (SOP) and water evaluation and planning (WEAP) model. The results indicate that the combination of fuzzy logic and hedging rules in a many-objectives system is more efficient than the discrete hedging rule alone. For instance, the reliability of the hydropower requirement in the fuzzified discrete hedging method in a drought scenario was found to be 0.68, which is substantially higher than the 0.52 from the discrete hedging method. Moreover, reduction of the maximum monthly shortage is another advantage of this rule. Fuzzy logic reduced 118 million cubic meters (MCM) of deficit in the Karun-3 reservoir alone. Moreover, as expected, the non-hedging SOP and WEAP model produced higher reliabilities, lower average storages, and less water losses through spills.

The Climate Challenge in Managing Water: Evidence Based on Projections in the Mahanadi River Basin, India

This study analyzes the long-term changes in the rainfall and surface hydrology of the upper and middle sub-basins of Mahanadi, an inter-state river basin in eastern India that experiences climate-induced hydrological extremes, and draws implications for the sustainability of irrigation and drinking water supplies. The likely impacts of rainfall changes on surface flow were also modeled. A Water Evaluation and Planning (WEAP) model was set up (beginning June 2009 and ending May 2050) to analyze the future water balance of the basin for the expected changes in socio-economic conditions. The model was also run for future scenarios that considered different water management interventions, and hydrological consequences of climate variability and change. The model results showed that there would be a water deficit, about 2,182 million cubic meters (MCM) by 2050 (20% of the demand) even under the business-as-usual scenario. The gap is expected to widen to 5,005 MCM (25% of the demand) under a high growth scenario. Further, the water demand management interventions in agriculture would be able to reduce the overall demand for water in the basin to some extent, while it would also reduce the supplies slightly due to a reduction in return flows occurring as a result of irrigation efficiency improvement. The water deficit under this scenario will reduce to about 2,773 MCM in 2050. Under the predicted changes in climate, the water deficit is expected to reduce further (will be 1,684–2,373 MCM in 2050) due to an increase in supplies owing to an increase in the catchment yields resulting from higher rainfall. While there will be a significant amount of outflow from the two sub-basins in all the scenarios in most future years (ranging from 25,286 MCM to 28,697 MCM in 2050), during drought years, the water deficit in the upper basin areas will increase slightly, but with a significant reduction in the outflows to the lower sub-basin areas by 2046–47 (will be about 11,311 MCM). These results indicate that there is a need for building more water storage/diversion infrastructure to detain floodwaters during wet years that can provide buffer storage for the dry years.

Evaluation of the WEAP model in simulating subbasin hydrology in the Central Rift Valley basin, Ethiopia

Background The subbasin hydrologic behaviors have been altered by many natural and anthropologic factors such as climate change and land development activities. Model-based assessment can be used to simulate both natural hydrological processes, human-induced effects, and management strategies on water resources. For the Ketar subbasin, the WEAP (water evaluation and planning) hydrologic model was developed that aimed at (1) evaluating the application of the WEAP model in the Ketar subbasin, (2) evaluating the demonstration of the WEAP model using model efficiency evaluation criteria, and (3) simulating hydrological processes of the subbasin using the WEAP model. Methods WEAP-based soil moisture method (rainfall-runoff) hydrology routine is comprised of a lumped, one-dimensional, two-layer soil water accounting that uses empirical functions to designate evapotranspiration, surface runoff, interflow, and deep percolation for a sub-unit at root zone. A catchment is considered as the smallest hydrologic response unit. The catchment’s surface hydrological balance is typically estimated by discretizing the catchment into multiple land uses for which water balance is estimated at root zone. Results The monthly measured and simulated streamflow statistics showed a positive strong relationship with R2 of 0.82, NSE of 0.80, and IA of 0.95; and with R2 of 0.91, NSE of 0.91, and IA of 0.98 for calibration and validation periods respectively. Similarly, the mean monthly measured and simulated streamflow showed an agreement with R2 of 0.99, NSE of 0.97, and IA of 0.99, and R2 of 0.94, NSE of 0.93, and IA of 0.93 for the periods of calibration and validation respectively. Conclusion The model has demonstrated the capability to represent the hydrologic dynamics of the subbasin both at monthly and mean monthly periods. In general, the overall model performance evaluation statistics show a very good agreement between measured and simulated streamflow at the outlet of the subbasin.