The Impact of Climate Variability and Land Use Changes on Hydrological Ecosystem Services: A Case Study of the Dassari Catchment, in Northern Benin

Abstract

Water is the most essential component for terrestrial ecosystem functioning and it provides different types of hydrological ecosystem services. Beyond the quantification of the hydrological ecosystem services, this work investigated the impacts of climate variability and different land use type on hydrological ecosystem services, water qualities were also assessed as a service.

The study was carried out in the Dassari catchment (192 km2) which is nested into the Pendjari basin at Porga outlet, North West Benin, where land degradation has increased over the years due to the high pressure on land. Therefore, the hydrological ecosystem services were firstly analysed according to households’ knowledge and perception. Trend analyses were performed on past and future rainfall and temperatures to assess climate variability in the Dassari catchment. The effects of climate variability and land use on the hydrological ecosystem services were evaluated using a distributed hydrological model J2000 and GISCAME which is a web-based software that has three components: a Geographic Information System, a Cellular Automaton, and a Multi-criteria Evaluation). Groundwater quality was also assessed by analysing the physical and chemical qualities of groundwater samples. These parameters’ values were compared to the past values from the General Water Office of Benin and withWorld Health Organization DrinkingWater Standards. Lowlands were found to be an important source of hydrological ecosystem services provision and their cultivation was found to contribute to income levels of farmers at 24.4 _ 19 %, 7.8 _ 3.5 % and 2.3 _ 2.25 %, respectively, for poor, moderate and rich households per year. The analysis of the effect of climate variability on the hydrological ecosystem services showed that, in the future, there will be a considerable decrease of runoff (20 to 45 %), mainly because of the decline of precipitation (16.1 %) considering the scenarios of business as usual (A1B). The same trend was observed for groundwater recharge. This decrease was quite low with the climate scenario of sustainable development (B1).

Furthermore, in areas mixed forest, open woodland and shrubland were the dominant land cover, groundwater recharge is increased while the surface runoff decreased. The contrary effect has been observed where agricultural land is the dominant land use. The chemical analysis of groundwater indicated that groundwater quality in the Dassari catchment is still good according World Health Organization Drinking Water Quality Standard, However, a significant change was observed in nitrate concentration (4.4 to 24.9 mg/l in 6 or 7 years) which is considered as an indicator for anthropogenic impact.

This study shown that future climate variability will have a negative impact on the hydrological ecosystem services and also, agricultural lands were found to contribute to the decrease of the hydrological ecosystem services. To mitigate this situation, more attention must be given to the development and adoption of sustainable ecosystem management that meet the needs of hydrological ecosystem services end-users.