Spatiotemporal effects of wastewater ponds from a geoenvironmental perspective in the Kharga region, Egypt

Abstract

One of the major geoenvironmental problems in the Kharga region arises from the haphazard exploitation of groundwater resources and sewage dumping, which have resulted in wastewater accumulation in the form of ponds. The impact of the spatial expansion of wastewater ponds in Kharga and the surrounding area has been so pervasive that ponds have become a source of environmental degradation. These ponds are distributed throughout the area, but the major lakes are located in the eastern and southeastern provinces. The water levels of these ponds are rising at a remarkable rate, especially in the winter, when there is no evaporation and rainfall can lead to overflows that flow towards cities, villages and farmlands. As a result of untreated sewage inflows, all the low surrounding spaces are at high risk of being influenced by these ponds. The objectives of this study were to evaluate the spatiotemporal threats posed by wastewater ponds and develop a conceptual model to estimate the geoenvironmental impacts on the surrounding areas. GIS and remote sensing were used to process all available geological, topographical, hydrogeological, hydrological, land use and environmental data. The pond expansion trend was estimated from Landsat time series from 1984 to 2018, and the results indicated that the wastewater bodies continuously increased and the land cover percentage decreased. The encroachment of wastewater ponds has resulted in extensive land cover disturbances in recent years, and land use change has affected nearly 2.5% of the region. The complexity of the problems associated with wastewater ponds in the Kharga district requires a comprehensive management plan that is effective in not only maintaining the stability of the ponds but also in improving the sociocultural and economic conditions around the ponds. Specifically, the wastewater drainage and accumulation system should be managed according to the surrounding functional context.