Impact of artificial destratification on water availability of reservoirs in the Brazilian semiarid

Abstract: Field surveys and integral modelling were carried out to study the effect of bubble plumes on the flow hydrodynamics and the time-evolution of water temperature profiles in a shallow lake with maximum depth of about 4 m. Then, model simulations were performed to verify the feasibility of destratification of ten water-supply reservoirs with capacities of 10-2,000 hm3. Finally, hydrological modelling was conducted to assess the impact of destratification on evaporation suppression and its effects on reservoir yield. The results indicate that net temperature reductions of the order of 1.0°C can be obtained, which corresponds to evaporation suppressions of approximately 10%. In turn, this resulted in increases in the regulated flow of 2-12% that could be described by a general correlation. Lastly, a simplified feasibility analysis provided an operational cost of about 1.0 US$ per cubic meter of saved water, which suggests that artificial destratification cannot be discarded as an alternative for supplementing water supply in rural water-scarce regions.摘要：针对最大水深约4米的浅水湖泊，开展野外实地调研与积分建模研究，以探究气泡羽流对流动水动力学特性以及水温廓线时间演化过程的影响。随后，针对库容为10~2000 hm³的10座供水水库，开展模型模拟以验证其水体消分层（destratification）的可行性。最后，通过水文建模评估消分层对蒸发抑制的作用，以及其对水库可供水量的影响。研究结果表明，可实现约1.0℃的净降温幅度，对应蒸发抑制率约10%，进而使得调控流量提升2%~12%，该变化可通过通用相关性公式进行描述。此外，简化可行性分析显示，每立方米节约水量的运行成本约为1.0美元，这表明在农村缺水地区，人工消分层作为补充供水的备选方案不应被舍弃。