Hydrological modelling and evolution of lakes and playa-lakes in southern Spain constrained by geology, human management and climate change

Abstract

The hydrological functioning of wetlands in S Spain is poorly understood. We perform a 22-years hydrological modelling of seven playa-lakes located in a semi-arid region of southern Spain, including dry and wet periods. To do that, we applied a hydrological balance model to reconstruct past lake water levels. In addition, we investigated the hydrochemistry of the water, the basin bathymetry, and the geological setting of the watersheds, acquiring new lithology and active structures data. Once the models were constrained, scenarios considering increases on temperature and human management were implemented, and discussed. The water balance is simplified to precipitation (water input) and basin discharge (evapotranspiration), as the lakes are disconnected from groundwater because of the low-permeability substrate. In addition, unlike in previous studies, we add overflows to the modelling. The results of the model agree with actual lake water monitoring data (R2 > 0.8). We observed that the hydroperiods of some of these lakes vary from permanent lakes to ephemeral, depending strongly on the basin bathymetry. Lakes with steeply margins show longer hydroperiods, whilst it is shorter for low-lying floor playa-lakes. In addition, we observed that steeply lake margins respond to active faults and/or lithological changes. To forecast the effects of climate change on the lake hydroperiods, we applied a 1 °C increase in average temperature in our hydrological modelling. The hydroperiod is significantly reduced for ephemeral playa-lakes, whilst is barely affected in permanent lakes. Moreover, we detected the high sensitivity of ephemeral playa-lakes to the anthropogenic management, including siltation, plant colonization and changes watershed surface.