Effects of temperature change on water discharge, and sediment and nutrient loading in the lower Pearl River basin based on SWAT modelling

Abstract

The impact of climate change on hydrological processes and nutrient input is one of the major uncertainties in projecting future global warming. The Soil and Water Assessment Tool (SWAT) model is applied to simulate the effects of temperature on the hydrology and sediment and nutrient load in the lower Pearl River Basin, South China. Calibration and validation results for SWAT showed that the Yamen estuary is appropriate for simulating the impacts of temperature change on both hydrological processes and nutrient input. The possible temperature change scenarios were set at T-2, T-1.5, T-1, T-0.5, T+0.5, T+1, T+1.5, T+2, T+2.5, T+3 • C compared to the current temperature, T• C. The results showed that the relative variation of discharge with temperature was slight. The sediment load at T+3• C is increased by 13.58% compared to that at T • C. Inorganic N and P inputs to the Yamen estuary showed an increasing trend with the temperature increase from T-2• C to T+3 • C. Global warming can reduce the vegetation land cover by slowing plant growth, which will aggravate the water and soil loss. Temperature changes would have an effect on mineralization and nitrification by changing soil temperature and temperatures. The warming is projected to cause an increase of sediment and nutrient load into the estuary and accelerate eutrophication in the coastal area.

Assessing ways to combat eutrophication in a Chinese drinking water reservoir using SWAT

“…Representation of monthly average flow was also satisfactory (ENS: 0.80-0.91), where ENS values in other Chinese studies have been reported to range between 0.63 and 0.93 for the monthly average flow (e.g. Li et al 2011). During calibration of hydrology several parameters were changed specifically for each soil layer and land use type, but also globally (Table 8).…”

“…SWAT has been used in several studies in China to assess impacts of climate changes, land-cover changes and land use (e.g. Ouyang et al 2008;Li et al 2011) on hydrology and, to some extent, on nutrient export. However, to incorporate the connectivity between watersheds and reservoirs, we expanded the ordinary SWAT-watershed approach by coupling it with a simple, but widely used, empirical equation to estimate total phosphorus (TP) concentrations in the reservoir (Vollenweider and Kerekes 1982) for use as a proxy of trophic status.…”

Distinct effects of temperature change on discharge and non-point pollution in subtropical southern China by SWAT simulation

“…The parameters FL, SD, IN and TP decreased as temperature rose, while N3 increased slightly. However, the situation was different for the DWR, where FL changed very slightly, while SD increased strongly or decreased slightly, respectively, when temperature rose or dropped (Li et al 2011). The parameter IN showed a significant increasing tendency under climate warming scenarios (Li et al 2011).…”

“…Previous research by the authors (Li et al 2011) revealed the effect of temperature change on water discharge and nutrient loading in the downstream area of the Xijiang River (Downstream of West River, DWR). Because the regional patterns of change in hydrological processes under warming were very complex, in this study we compared the UER with the DWR to check whether temperature change had a similar effect on two watersheds in close proximity.…”

“…Precipitation as snow is very rare in this region. The difference in climate might result in a distinct regime of seasonal response to climate warming (Li et al 2011). A simulation study in the humid tropics has projected streamflow to decline slightly in summer under the A2 or B2 emissions scenarios (Raneesh and Santosh 2011).…”