Evaluating flood regulation ecosystem services under climate, vegetation and reservoir influences

Abstract

Abstract Flood regulation is one of the critical ecosystem services that people acquire from ecosystems. With climate change and variability and land use/land management, ecosystem services have changed globally. Some ecological restoration activities, such as the Grain for Green program (GGP) implemented in the Yellow River basin (YRB) of China, greatly change the flow patterns and affect the flood regulation services provided by ecosystems. Many studies have assessed the peak flow trends in the YRB; however, quantitatively evaluating flood regulation services while also considering the effects of climate, vegetation and dam construction is rare. In this study, the annual flood regulation index (FRI) was calculated from 1958 to 2014 for nine watersheds in the YRB using an index-based ecosystem service approach. Based on the community land model coupled with the geomorphology-based hydrological model (CLM-GBHM) established in the YRB, the annual FRI under two vegetation scenarios, i.e., (1) static leaf area index (LAI) in 1982 and (2) remotely sensed LAI from 1982 to 2014, was calculated. The effects of changes in climate and vegetation on the flood regulation services were then assessed. The Impacts of reservoirs were also discussed based on the FRI calculated using observed data. The results indicate that the annual FRI generally improved in most areas of the YRB over a 57-year period. The annual FRI significantly increased in the upper YRB while being stabilized in the headwater basin, primarily benefitting from the regulations by the Longyangxia and Liujiaxia reservoirs. When climate change was considered as a single influencing factor, the flood regulation services were negatively affected by extreme precipitation. Impacted by the increased total wet-day precipitation (PRCPTOT) and the average rainfall intensity (SDII) in the flood season, the mean annual FRI significantly declined by 6.3%–33.8% among the studied watersheds during 2000–2014 compared to those from 1980 to 1999. Positively impacted by the vegetation restoration after the GGP was implemented in 1999, the mean annual FRI increased 8.6% in the regions above Lanzhou station and 1.6%−5.5% in the five tributaries during 2000–2014. Our results suggest that the negative influences of the FRI from extreme precipitation should be considered under climate change, while improving the flood regulation ecosystem services through implementing vegetation restoration programmes can enhance flood risk management in other river basins.