Evaluation of soil hydrophysical parameters along a semiurban small river: Soil ecosystem services for enhancing water retention in urban and suburban green areas

Abstract

Urban green areas are subjected to distinct environmental conditions, and plants are exposed to numerous adverse factors. Urban areas are characterised by extensive hardened surfaces, paved or covered by asphalt, which are practically impermeable to water. Appropriate maintenance of ditches and rivers—an issue that has been neglected in recent times—is key for increasing the water-holding capacity of urban soils. Various human activities also adversely affect rainwater retention in urban soils; the transformation of the landscape by urban development changes hydrographic conditions quite radically. This study investigates the hydrophysical conditions and evaluates the variability in water retention capacity of urban (a designed river park), suburban, and rural soils in and around Kraków, Poland. This evaluation is based on hydrophysical measurements in the topsoil and in soil layers below 100 cm. Based on the distribution of water-retention parameters, we found that during the period of investigation, the soil water content at the urban site was comparable to that at rural farmlands. The factors most decisive for water retention in the soil were the soil bulk density and hydraulic conductivity. Multivariate analysis of variance showed that soil compactness influences water retention in urban soil and also the permanent wilting point (PWP, pF = 4.2). These results can inform the evaluation of periodic water supply shortages in urban water-soil systems. Subsequent studies should focus on effective ways to improve water retention in urban soil. Water storage in soils will be an important ecosystem service in many cities where the water table is lowered due to drought and/or the urban heat island effect.