Utilization status of rainwater harvesting and its improvement techniques in bare karst areas for domestic use and ecological restoration

Abstract

Water imbalances remain the primary problem from the past to the coming future in karst area of South China. A well-admissive method to cope with drought and flood problems is under searching. Rainwater harvesting by water tanks has being an approved way to alleviate water shortage, but with some defects such as bad water quality, unstable sources, and limited volume. To find out its running status, 50 water tanks in a part region of Fengshan County were surveyed. One of them was chosen for online-monitoring and 25 water tanks were sampled for chemical analysis. The results show that there were three typical problems during its running. First, water tanks usually get dry in rainless months, especially in extremely drought events. Second, water quality declines once water has stored for about 100 days with no new supplement. The deterioration of water quality is related to the long-preserved time rather than exogenetic pollution. Third, the situation becomes more serious under the pressure of climate change and the rocky desertification. Therefore, a new rainwater harvesting strategy is proposed for improving this situation. The conception site model (CSM) in hill slope for tank location selection is the critical point, since water harvesting for tanks depends on slope characters. As a CSM example, the hillslope hydrology related to the overland flow, the resurgence of flow in epikarst, and vadose flow at Yaji Karst Experiment Site were investigated to illuminate the complexity of hydrological process and diversity of flow pattern. Then, it is suggested to make full use of different flows from slopes, especially to increase the availability of vadose flow. Finally, besides drinking purpose, water tanks should be extensively used for irrigation and reforestation to obtain economic return and support its maintenance.