Application of the InVEST Model to Quantify the Water Yield of North Korean Forests

The calculation and mapping of water yield are of significant importance to the effective planning and management of water resources in North Korea. In this study, we quantified and assessed the water retention capacity of North Korean forests using the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) water yield model; six thematic maps were constructed and two coefficients were derived for use in the modeling. Data were obtained from the following sources: average annual precipitation from WorldClim; average monthly evapotranspiration from Global Potential Evapotranspiration (Global-PET); and the soil depth data from the International Soil Reference and Information Centre (ISRIC). The plant available water fraction was calculated using a bulk density formula. Land cover was classified using the Normalized Difference Snow, Water and Vegetation Indices, using Moderate Resolution Imaging Spectroradiometer (MODIS) satellite imagery. Data for the watershed analysis were provided by the World Wildlife Fund. The total water retention in North Korean forests was estimated to be 760,145,120 tons in the 2000s. However, previous studies from 2011 showed a much higher (by 9,409,622,083 tons) water retention capacity in South Korea. In North Korea, the largest monthly water storage volume occurred in July, followed by August, September, and June. This mirrors rainfall patterns, indicating that precipitation has a significant impact on water storage. Analysis of the annual spatial distribution of water storage by administrative district showed that Hamgyongnam-do had the highest, followed by Jagang-do and Gangwon-do Provinces.