Hydro-climatic extremes: trends, anomalies and implications for urban water management

ABSTRACT Assessing the trends and anomalies of hydro-climatic extremes for improving the urban water managment. Intensifying hydrological and climatic risks are threatening infrastructures and services; therefore, understanding anomalies in hydro-climatic extremes (HCE) is imperative for sustained infrastructure/services. This study investigates the dynamics of HCE and implications for urban water management, with a case of Pokhara Metropolis (Nepal). The city faces recurring challenges from excessive stormwater and streamflow, water scarcity and loss of life. To assess the HCE trends, this study applied Indicators of Hydrologic Alteration (IHA) and ClimPACT2, for both baseline and projected scenarios to streamflow, precipitation and temperature data. The HCE were characterized by coupling indices from the Expert Team on Sector-specific Climate Indices (ET-SCI), IHA parameters and Standardized Anomaly Index (SAI). Results reveal a likely excessive increasing trend in future total annual precipitation (e.g., 0.98–18.32 mm/year at Pokhara Airport) along with severe wet conditions and temperature changes resulting in severe hot SAI, thereby, challenging water supply and public health. Consistent with climatic extremes, extremely wet streamflow is projected to increase (max. monthly flow from 224.00 to 351.10 m3/sec). This study underscores a need for term-based strategies to capture opportunities from HCE for improving water management, which ultimately supports achieving the goals of Nationally Determined Contributions and sustainability (SDG 6, SDG 11, SDG13).