Discussion
IPCC (2018) indicated that global warming was predicted to increase by
1.5 °C by 2050’s compared with the present situation. Hydrological cycle
and water quality will be affected by global warming (Anand et al.
2018). The generation of proper
water management plans depends on interdisciplinary approaches and
modeling studies of direct and indirect effects of climate change on
drinking water resources (Qiu et al. 2019). Water management strategies
for drinking water basins must be developed based on climate change’s
effect on water quality and quantity (Garnier and Holman 2019). It is
difficult to meet good quality water demand for public health since the
world population until 2050 will increase 9,7 million, so this will
increase world water demand by 20-30 % (UNESCO, 2019). Land uses-covers
and climate change are the main factors of water quality and quantity
degradation globally (Giri and Qiu 2016; Su et al. 2016). The
preparation of better water management policies is based on both land
use-cover and climate change impacts on non-point pollution sources and
streamflow (Mello et al. 2018). Although domestic legislation has been
conducted to provide sustainable drinking water management in many
countries, measures in that legislation haven’t been determined based on
adaptation to climate change and for understanding the patterns of water
use under different land-use/cover policies (Wang et al. 2018; Clerici
et al. 2019; Trolle et al. 2019). In Turkey, based on the Regulation on
Protection of Drinking and Utility Water Basins (PDUWB 2017),
site-specific drinking water management plans have been generated.
However, these studies don’t include climate and land use- cover change
policies. Moreover, although these studies cover many measures,
especially the restriction of agricultural activities and protection of
forest areas, the effects of these measures on streamflow and NPS have
not been examined. This study is an example of land-use/cover and
climate change effects on streamflow and NPS to generate accurate water
resources management. Climate change scenarios, RCP 4.5 and RCP 8.5, and
land-use scenarios, conversion of shrubland to the forest and conversion
of agricultural areas to the forest, were combined to show their impacts
on flow rate and NPS pollutants to generate future proper water
management plans. Study results show that conversion of agricultural
areas to the forest under RCP 8.5 has more impacts on streamflow and NPS
pollutants. This situation indicates that land-use planning and
restrictions in drinking water basins require examining land-use/cover
and climate change effects on water resources and NPS pollutants to
protect drinking water resources for public human health.
Moreover, this study also shows that modeling studies and statistical
assessments of modeling results are important to evaluate these effects
while studying these effects on water resources and NPS pollutants since
combining modeling and statistical assessments give whether or no
significant effects of these changes.