Investigation of hydrologic carrying capacity and associated water productivity for water resources allocations: a case of kilombero river catchment, tanzania
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Date
2025-07
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NM-AIST
Abstract
The world over, water resources availability is in decline while population and associated water demands are in an increase. This limits the capacity of hydrologic catchments to sustain the growing economic activities. In this regard, the productivity value of water (PVW) is increasingly gaining popularity among water resources managers as a tool for water allocation. Studies on PVW help to complete the Integrated Water Resources Management Pillars i.e., the famous 3E’s (Equity, Economic/Efficiency and Ecological Integrity) by assessing the value of water beyond just the equity principle that only concentrates on the fair volumetric share of water. However, PVW concept is at its nascent stage characterized by a lack of a knowledge and tools to relate water resources and the economy it propels. The current study therefore, began by assessing catchment hydrologic carrying capacity and delved into assessing PVW after which a marginal productivity of water (MPW) was assessed to determine increasing or diminishing return for every change in water use. These were preceded by an analysis of hydrologic carrying capacity of the catchment where non-parametric Mann-Kendall (MK) statistical tests as well as the Soil and Water Assessment Tool (SWAT) were applied. These helped to assess climate trend and model the interaction of hydrology, climate and land use/cover changes and their implication to water availability. The results showed that the historical hydrologic parameters were favorable whereas the future painted a stressful scenario (p<0.05). Given the increased expansion of thirsty sectors of economy, the seemingly increasing river discharge at Swero (1KB17) gauging station was attributed to sediment deposition with annual loos of 42.13 Tonnes/Ha in 2021 to a projected sediment loss of 43.95 Tonnes/Ha in 2041. Furthermore, findings on productivity of water showed that paddy had low PVW (0.01 USD/m3) compare to Sugarcan (0.10 USD/m3) and Hydroelectric production (0.19 USD/m3). However, the sub-sector is the most impactful in terms of food and employment
security. On these bases, deliberate support and protracted capacity building and advocacy for the rainfed system of rice intensification (SRI) is recommended as a plausible paddy farming system which also had good PVW (0.11USD/m3). This study also recommends assessment of the value of water for the environment as an important sector as well as across the value chain for all sectors. Finally, the study recommends improvements in enforcing both water and LULC plans to ensure controlled expansion of economic activities that sustains the catchment performance.
Sustainable Development Goals
SDG-2:Food security, paddy farming, SRI
SDG-6:Water-use efficiency, IWRM, PVW
SDG-7:Hydropower water productivity
SDG-8:Economic valuation, employment
SDG-9:Modeling tools, planning insights
SDG-12:Resource productivity, land management
SDG-13:Climate trends, modeling, adaptation
SDG-15:Ecosystem integrity, sediment control