Multipurpose reservoir performance analysis: a case study on the Billings sub-basin

As a result of economic development, multiple and extensive uses of water resources have caused an imbalance between the demands and the water supply in reservoirs. Thus, the present study analyzed the performance of the Billings Reservoir, located in the Alto Tiete basin - So Paulo, in terms of meeting the demands of urban water supply and electricity generation simultaneously. For that, three operating scenarios for the Reservoir were considered: the first, different numbers of water transfer and fixed consumptive demand were adopted; in the second, the transfer of water was suppressed and different consumptive demands were considered; the third, used the indirect potable water reuse as an aid to recharge the Reservoir and considered different consumptive demands. The statistical performance indicators reliability, resilience, vulnerability and Water Sustainability Index were calculated. And based on the results obtained for Scenario 1, the curve of performance criteria versus reservoir pumping, reliability, resilience, and water sustainability index increased and vulnerability in the system reduced significantly. The Scenario 2, according to the curve of performance criteria versus demand flow, demonstrated that the increase in water demand implies significant reductions in reliability, resilience and water sustainability, and reflects in the increase of system vulnerability. Finally, the Scenario 3 demonstrated that the recharge of the reservoir when employing reuse water provides improvements in reservoir performance compared to Scenario 2 and promotes the reduction of environmental impacts from the release of the sewage system into Billings. It was possible to observe the relevant role of the water supply to the Billings Reservoir, in terms of meeting its demands and water sustainability when adopting the multiple use of water.