Estimated Forest Ecological Water Requirements in the Jinghe Watershed—Theory and Case Study

Abstract

The ecological water requirement of forests is defined as the water resources used to maintain and improve the natural balance of forest ecosystems, which can be expressed by evapotranspiration of trees during the growing season. The relationship of evapotranspiration and soil moisture of forestland with tree growth showed that, if the soil moisture was above the temporary wilting point or the point of growth retardation, the growth of trees can, respectively, be basically or normally sustained. Therefore, they can be taken as the minimum and the suitable ecological water requirements of the forest. These points can be estimated by introducing the soil factor ( K_s) and tree species factor (K_t) to potential evapotranspiration with the Penman formula. With geographic information system (GIS), the ecological water requirement for forests in the Jinghe watershed, western China was estimated. The results revealed that the minimum and suitable ecological water requirements of the forests in the Jinghe watershed were approximately 204×10⁷ and 340×10⁷ m³, respectively.