Spatial and temporal changes of water supply and water conservation function in Sanjiangyuan National Park from 1980 to 2016

Spatial and temporal changes of water yield and water conservation in Sanjiangyuan National Park were evaluated based on the InVEST model using seven periods of land use data from 1980-2016, meteorological data, soil data, and topographic data. The main conclusions were as follows:(1) The annual precipitation in Sanjiangyuan National Park showed an insignificant increasing trend from 1980 to 2016, while the potential evaporation and actual evaporation increased significantly, with increase rates of 14.46 mm/10 a and 5.95 mm/10 a, respectively. In this context, the water yield and water conservation in Sanjiangyuan National Park showed an insignificant increasing trend, with an annual average value of 118.17 mm and 45.04 mm, respectively. The total water resources in Sanjiangyuan National Park experienced a process of drastic decrease-increase-slight increase. Precipitation, actual evapotranspiration, and actual evaporation ratio(actual evaporation capacity) were the main climatic factors affecting water yield and water conservation.(2) The spatial distribution of water yield showed a trend of decreasing and then a trend of increasing from north to south. Among the three parks, Precipitation was highest in Lancangjiangyuan Park.This park also had relatively high vegetation cover. Hence, the water yield quantity was relatively higher. The water yield in Huangheyuan Park showed an obvious increasing trend from north to south due to the climate difference. Changjiangyuan Park had the lowest precipitation of the three. However, the evapotranspiration coefficient of bare land and desert was low and the actual evaporation was also low. Hence, water yield in this region was slightly higher than that of Huangheyuan Park. The spatial distribution of water conservation was consistent with that of water yield and also affected by topographic indices. On the whole, the spatial distribution of water resources was mainly caused by spatial differences of precipitation and evapotranspiration, which are closely related to land cover and soil characteristics.(3) The amount and spatial distribution of water yield and water conservation in the park varied significant in extreme precipitation conditions. In Huangheyuan Park and Lancangjiangyuan Park, the water resources in a dry year were 40%-45% those in a wet year and 58%-75% of the annual average values. In Changjiangyuan Park, the water yield in a dry year was only 29.08% that in a wet year and less than half the annual ave