Assessment of water resources availability and demand in the Mara River Basin

- We modeled space-time variability of water resources and demand in Mara River Basin.
- Water resource status evaluation model is proposed.
- Critical sites and months of water shortage are identified.
- The Mara-Serengeti ecosystem is highly vulnerable to water shortage.
- Irrigation and tourism are the largest and smallest water demands, respectively.

A simple model was developed to assess space-time relationships of water resource availability and demand in data limited watersheds. The model used a defined index method to evaluate water resource status with respect to anticipated demands. Input data requirements and data processing steps and strategies were discussed. The model takes outputs from a hydrologic system model and demand estimates and compares supply-demand relationships on the basis of expected percentage of demand satisfaction for the basin of interest. Space-time matrices were used to display results of the model for ease of understanding and decision making. The model was customized and applied for the Mara River Basin (MRB) to assess water resource availability and demand. Assessment of water resources in blocks of water use using indicators of the growing water demand among competing sectors threatening the sustainability of communities and ecosystems in the basin. The spatial and temporal distribution of water resources and the corresponding demand were quantified. Twelve distinct sub-basins were defined in the basin and their water availability was assessed based on long term rainfall-runoff simulation using the Soil and Water Assessment Tool (SWAT). Water demands from six consumptive sectors were divided into three classes and compared with a corresponding three classes of monthly water availability. Results have shown significant variability of water availability and demand in the MRB. Further study on possible quantitative indicators to redistribute water among stakeholders may assist in improving water management.