Effects of the Grain for Green Program on the water ecosystem services in an arid area of China—Using the Shiyang River Basin as an example

The Grain for Green Program (GFGP) is one of the largest land restoration/afforestation and one of the most ambitious ecosystem conservation programmes in the world; the programme has altered the land-use pattern and exerted a significant influence on the ecosystem services. Water ecosystem services are important for arid and semiarid China, however, few of the researchers tried to quantify the effect of GFGP on water ecosystem services. The Shiyang River Basin is one of the key areas of GFGP implementation in the arid region of northwest China. We used the integrated valuation of ecosystem services and trade-offs (InVEST) model to quantitatively evaluate the changes in water yield and water conservation of water ecosystem services during the implementation of the GFGP from 2000 to 2015. The results indicate the following: 1) Land use/cover patterns in Shiyang River Basin have changed dramatically after the implementation of GFGP. Forest and grassland has increased significantly. 2) The average water yield depth and the total water yield decreased from 56.4 mm/year to 55.89 mm/year and 22.88 × 108 m3/year to 22.68 × 108 m3/year, respectively, and the average water conservation capacity and total water conservation increased from 16.90 mm/year to 17.99 mm/year and 6.86 × 108 m3/year to 7.30 × 108 m3/year, respectively. 3) The total water yield and total water conservation of forest and grassland increased, due to the increasing area of forest and grassland. 4) Thanks to the adoption of relatively rational land-use conversion patterns, at regional scale, the implementation of GFGP improved water conservation and did not result in a significant reduction of water yield in Shiyang River Basin. Results underline the importance of selecting appropriate land-use conversion types in order to achieve sustainable provision of ecosystem services at the regional scale.