Soil Conservation Service-Curve Number method-based historical analysis of long-term (1936-2016) temporal evolution...

Managing groundwater resources in urban areas requires an adequate understanding and assessment of urban hydrogeological systems (structure, components, connections, and imposed conditions) as a part of a larger, dynamically evolving environment. Urbanization and climate change are amongst the widely recognized signs of such a continuous evolution. Within this context, the present study gives a quantitative assessment of the impact of these two factors threatening water resources in urban environments. The Soil Conservation Service-Curve Number (SCS-CN) method is used to conduct a long-term quantitative analysis of the temporal evolution of the potential natural groundwater recharge from precipitation at the scale of Algiers city for an 80-year-long period (1936-2016). The length of the study period allowed us to account for and analyze important changes in urban settings and climatic conditions within the study zone. Overall, two trend shifts over three distinct periods were found to characterize the temporal evolution of precipitation, several climate change indicators defined for the study, and the potential natural aquifer recharge. A strong, approximately 1:4, linear correlation between the estimated city-scale potential natural aquifer recharge and precipitation was observed for the studied period (R² = 0.748). Moreover, even though the urban area has known a rapid (2nd order polynomial) increase from 1936 to 2016, climate change (accounted for via the changes in precipitation regime) impacted the city-scale potential natural groundwater recharge with higher magnitudes than urbanization. Finally, the computed climate change indicators show that starting in the mid-1980s, Algiers has started receiving less precipitations, with fewer heavy rain events and longer dry condition periods.