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 v 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 land 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.