ASSESSMENT OF WATER CONSUMPTION PATTERNS, LAND PRODUCTIVITY AND WATER PRODUCTIVITY IN KILOMBERO BASIN, TANZANIA USING WATER ACCOUNTING PLUS (WA+) FRAMEWORK

Abstract

This thesis attempts to implement the Water Account Plus (WA+) Framework to provide explicit geographic information on the process of water depletion and net withdrawal in a river basin. WA+ is a comprehensive yet straightforward and plausible water accounting framework that provides a consistent data collection and presentation system reflecting the overall state of water and land management within a river basin. WA+ analyses water loss rather than water withdrawals, and it goes beyond flow and runoff accounting. Rainfall is a known critical hydrological process in WA+, with only a portion of total rainfall transformed into streamflow and groundwater recharges. A substantial part of rainfall depletes directly through the processes such as ET from native vegetation, crops and rainfed plantations. The lack of natural water has a positive economic impact and provides many benefits. As a result, by just accounting for runoff, these benefits and uses of water will be discounted, and the overall view of water flows and benefits will be skewed. WA+ recognizes the impact of land use on the water cycle and provides a connection between water balance, land use, water use, and management options to change it by grouping land use classes with standard management features. Water availability, water degradation processes, beneficial and non-beneficial depletions, water and land productivity, and water withdrawals are covered by WA+. The WA+ Framework strengthens the perception of the current state of the basin, future, threats, and opportunities for change. It provides information that will assist management in making the basin more climate-friendly and responding to droughts and floods. It can be used to track changes in the basin's water supply and evaluate the consequences of potential measures like changing large-scale land use and expanding irrigated agriculture. A platform developed primarily to ensure the global applicability of WA+ by utilizing data from open-access satellite observations. This dissertation uses a case study from the Kilombero Basin to demonstrate how WA+ can be used. This study illustrates how the WA+ Framework may be utilized to offer much-needed explicit information on the state of water resources, scarcity and productivity. It uses limited ground-measured data and how accounting results may be used to identify vulnerability, capacity, and capacity and potential. According to the accounting results, the Kilombero basin is nearly closed, with more water being drained and half of the water depleted by processes that produce little or no benefit, i.e. non beneficial depletion. Excessive soil evaporation in shallow water table areas causes the bulk of these non-beneficial depletions. As a result, vast volumes of valuable freshwater resources are unnecessarily vaporized into the atmosphere. The findings also indicate that annual water depletion plus outflows in the basin surpass overall precipitation. Storage, particularly groundwater storage, has diminished as a result of this circumstance. A rapid reduction in groundwater storage, for example, may have severe consequences for the basin's long-term viability. The WA+ sheets were found to help determine the effect of various interventions.