The Impacts of Water Demand and Its Implications for Future Surface Water Resource Management: The Case of Tanzania’s Wami Ruvu Basin (WRB)

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.

Virtual Tracers to Detect Sources of Water and Track Water Reuse across a River Basin

“…The Water Evaluation And Planning (WEAP) system was used as the basic water resources model [36]. WEAP is a commonly used tool in strategic water resource planning and scenario assessment in many regions around the world (e.g., in [37][38][39]). WEAP uses the basic principle of water balance accounting, where total inflow equals total outflow, excluding any change in storage (in reservoirs, aquifers and soil).…”

Conserving Rivers and Their Biodiversity in Tanzania

“…Despite strong legal instruments for freshwater conservation, future changes in freshwater supply and demand in Tanzania will present challenges for balancing future river water allocations between ecosystems and human users. For example, Miraji et al [49] suggests that river flows in the Wami-Ruvu Basin are declining in part because of high rates of water withdrawals, which threatens numerous species of amphibians and reptiles. Current projections suggest that human demand for freshwater will substantially increase in the next decades.…”

“…The Wami-Ruvu, Lake Rukwa and Lake Nyasa basins may also be affected by SAGCOT projects. If surface water shortages ensue, recent studies [49,64] contend that groundwater abstraction may be encouraged as alternative for smallholders to continue irrigating their crops. Furthermore, recent work in the Kilombero Valley within the Rufuji Basin found reduced water quality (higher levels of turbidity, nitrate and ammonium) in streams used for irrigation within downstream sampling sites when compared to upstream sites [65].…”

Avaliação de Alocação de Água na Bacia Hidrográfica do Rio Inhanombe, Moçambique

“…Estudos recentes demonstraram que mudanças climáticas, desenvolvimento económico, crescimento populacional, captação extensiva de água, poluição da água e mudança no uso do solo são os principais desafios que alteraram o regime hidrológico natural na maioria das bacias hidrográficas de África, incluíndo a bacia do rio Umbeluzi (Juizo e Líden, 2010;Droogers et al, 2014), a sub-bacia de Didessa (Adgolign et al, 2015), a bacia do Drâa (Johannsen et al, 2016), a bacia do rio Mara ( George et al, 2018) e a bacia de Wami Ruvu (Miraji et al, 2019). A região sul de Moçambique tem sofrido nas últimas décadas desequilíbrios entre a disponibilidade e necessidades (CONSULTEC e SALOMON, 2009).…”

“…Isso leva a desafios no gerenciamento da demanda de água em regiões de rápido desenvolvimento devido à alta variabilidade espacial e temporal de recursos hídricos (Zeinali et al, 2020). As estratégias de gerenciamento de água do lado da demanda são mais acessíveis na mitigação de impactos de escassez, reduzindo as demandas anuais de água (Miraji et al, 2019).…”