Understanding the Water Quality Dynamics in a Large Tropical Reservoir Under Hydrological Drought Conditions

Severe drought is widely recognized for its impact on water quantity, but its equally consequential role in degrading water quality often goes understudied. This issue significantly complicates reservoir management, especially in multi-purpose reservoirs, which face potential conflicts between the water users during periods of reduced water availability. Despite numerous studies addressing water quality, there is limited data availability regarding the unique dynamics observed in semiarid regions. To address this research gap, an extensive data collection effort was conducted in a semiarid region reservoir serving multiple functions, including human consumption, irrigation, and fish farming. The primary objective was to establish a comprehensive database encompassing critical water quality parameters, facilitating an in-depth exploration of spatio-temporal water quality dynamics during a hydrological drought. The findings are expected to provide a solid scientific foundation for informed water management practices during severe droughts. Notably, the study reveals distinctive water quality dynamics in semi-arid regions. Monthly assessments confirm complete nutrient mixing within the studied reservoir, with temporal variations surpassing spatial ones, suggesting the applicability of complete-mixing models in future investigations. Additionally, the research underscores the prevalence of chemical stratification in dissolved oxygen levels over thermal stratification, with dissolved oxygen declining downstream, particularly during the rainy season. In summary, this study offers a comprehensive understanding of water quality dynamics in a reservoir experiencing significant degradation during a hydrological drought, highlighting the vulnerability of semiarid reservoirs to water quality decline during such periods. These insights hold substantial importance for enhancing management strategies and mitigating water conflicts in similar tropical reservoirs, thereby contributing to the sustainable utilization of this critical resource.