Modelling and assessing the impact of illegal water abstractions by upstream farmers on reservoir performance

Authors : Nura Jafar Shanono, John Ndiritu

Pages : 47-54

Doi:10.48053/turkgeo.1011374

View : 19 | Download : 14

Publication Date : 2021-12-15

Article Type : Research

Abstract :This study proposes a reservoir yield analysis that incorporates the realities of upstream illegal human activities relating to water abstraction. The study assesses the impact of such unlawful human activities on reservoir storage and yields quantitatively. A reservoir operation water balance model was simulated and coupled with upstream irrigation users’ propensity to unauthorized water abstraction and set to co-evolve for the entire simulation period. The model was developed using four-state drivers (hydrological state, users’ compliance, management competence and reservoir performance). The impact of human behaviour (users’ and management) was assessed using 9 plausible human behaviour scenarios. The model was applied to a system of 5 reservoirs using the 90-year historical hydrologic dataset. The trajectories of the storage, yield-demand and storage-yield ratios were analyzed under different human behaviour scenarios. Both storage and yield were found to substantially decrease as users’ compliance and management competence deteriorated for the same reservoir hydrological state. Depending on the scenario, the annual yield (%) was observed to reduce from 100 to 80 or 50 or even 30 of the annual demand due to changing behaviour. Also, most of the years in which the yield differs significantly from one scenario to the other are years with shallow storage due to drought. A yield difference of about 23% was recorded between the scenarios without and with the highest unauthorized abstractions. The study, therefore, revealed how human behaviour can significantly affect reservoir storage and yield performances. This highlighted the need to be incorporating the impact of unlawful human activities into yield analysis models to quantitatively assess the impact of human behaviour on reservoir performance.
Keywords : Farmers, Illegal water abstraction, Reservoir performance, Reservoir upstream