Abstract
River basins around the world face similar issues of water scarcity, deficient infrastructure, and great disparities in water availability between sub-regions, both within and between countries. In this study, different strategies under the Water Evaluation and Planning system (WEAP) were assessed to mitigate water overuse practices under the Current Trend (CT), Economic Growth (EG), and Demand Side Management (DSM) scenarios in relation to current and future statuses of Tanzania’s Wami Ruvu Basin (WRB). The results show that neither domestic nor irrigation water demand will be met based on the current trend. Under the CT scenario, the total water demand is projected to rise from 1050.0 million cubic meters in the year 2015, to 2122.9 million cubic meters by the year 2035, while under the DSM scenario the demand dropped to 990.0 million cubic meters in the year 2015 and to 1715.8 million cubic meters by the year 2035. This study reveals that there is a positive correlation between the highest surface runoff events and the highest unmet demand events in the basin. Terrestrial water demand alters the hydrological cycle of a catchment by modifying parameters such as surface runoff, particularly in small catchments. The results of this study prove that DSM strategies are more amenable to mitigate the impacts and implications of water demand, as they increase water sustainability and ensure ecosystem security by reducing the annual water demands and surface runoff by 15% and 2%, respectively.
Highlights
Over the period between 1962 and 2011, the global per capita freshwater stock declined by 54%, with decreases of 75% occurring in Sub-Saharan Africa (SSA), 71% in the Middle East and North
The Water Evaluation and Planning system (WEAP) model was conditioned to the year 2035 by introducing the three different scenarios (CT, Economic Growth (EG), and Demand Side Management (DSM)) over the entire simulation period
The results of this study reveal that DSM strategies would significantly improve water sustainability and ecosystem security, and would balance the supply and demand between upstream and downstream areas
Summary
Over the period between 1962 and 2011, the global per capita freshwater stock declined by 54%, with decreases of 75% occurring in Sub-Saharan Africa (SSA), 71% in the Middle East and NorthAfrica (MENA), 64% in South Asia, 61% in Latin America and the Caribbean, 52% in East Asia and the Pacific, and 41% in North America [1]. It has been noted that components of the terrestrial water cycle (groundwater, soil moisture, surface waters, snow, and ice) appear to be trending below previous ranges due to climate change, anthropogenic activities, and excessive water abstraction [2]. This is leading to large challenges in managing water demand in rapidly developing regions such as Africa, due to high spatial and temporal variability in the availability of water resources and limited amounts of total water availability across expansive semi-arid portions of the continent [3]. Recent studies have shown that climate change, extensive economic development, population growth, water pollution, and extensive water abstraction are the main challenges that have altered the natural hydrologic regime in most of Africa’s river basins, including the Sokoto Rima River basin [6], the Didessa Sub-basin [7], the Ouémé
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