『Abstract
The loss of nitrogen and phosphorus via non-point source (NPS)
pollution in the Jialing River Watershed has become the main pollution
sources of river waters in the Three Gorges reservoir area in
the past decades, while climatic conditions and human activities
directly affect changes of rainfall-runoff and land use types
which are closely related to NPS pollution. This study is to assess
the impact of climate change on hydrological behavior considering
future land-use types and rural residential area and their propagation
to NPS pollution loads. An integrated pollution load model composed
of regional climate, the Semi-distributed Land Use based Runoff
Processes (SLURPs) hydrological model and the improved export
coefficient approach within a single framework was explored and
developed to assess impacts of climate and land-use changes on
NPS pollution load. Climate data for the Special Report on Emissions
Scenarios (SRESs) future scenario B2 from Met Office Hadley center
were generated and used as the input data for the runoff and NPS
load evaluation of the Jialing River Watershed and the Markov
process used to forecast changes of land use types, respectively.
Simulations of present and future regional NPS pollution from
land use, livestock and poultry breeding, and agricultural population
over the Jialing River Watershed were performed to investigate
the potential impacts of global climate change on river water
quality using the established model. Results demonstrate that:
(1) Annual pollution load would obviously change due to variations
of runoff and livestock and poultry breeding, the largest growth
months in one year for total nitrogen (TN) and total phosphorus
(TP) load are both in June, which is accordance with changes of
rainfall amount. (2) The impacts of global climate change on pollution
load are relatively greater when compared to the impacts of future
livestock and poultry breeding increase or agricultural population
reduction; the effects from runoff increment leads to approximately
28.6% and 22.5% increases of TN and TP pollution load, respectively.
And (3) the impacts of land-use change have shown insignificant
effect due to soil conservation measures, whereas the impacts
of rural residential area account for great proportion changes,
of which about 5% of its increases are contributed to the increase
of livestock and poultry breeding; but the biggest contribution
rate is still from the output of different land use types. These
data will be useful and valuable in evaluating potential NPS pollution
load for the control of watershed pollution in the future and
understanding its migration and transformation in a large-scale
watershed where meteorological and underlying surface data are
mutative.
Keywords: Nitrogen; Phosphorus; Pollution load prediction; SLURP
hydrological model; Climate change; Jialing River Watershed』
1. Introduction
2. Data and methodology
2.1. Study area
2.2. Environmental databases
2.2.1. Environmental database for present scenarios
2.2.2. Environmental database for future scenarios
2.2.2.1. Meteorological data
2.2.2.2. Land use data
2.3. SLURP hydrological model
2.3.1. Principles of the SLURP model
2.3.2. Validation of parameters optimization and simulation
2.4. Forecasting model of NPS pollution load
2.4.1. The improved export coefficient method
2.4.2. TN and TP concentration and output coefficient
2.4.3. TN and TP dynamic coefficients into the river
2.5. Simulation scenario design
3. Results and discussion
3.1. Validation of the established model
3.2. Comparative analysis of monthly rainfall and runoff
3.3. Comparison of average monthly TN and TP load
3.4. Sources and contribution rates of average annual TN and
TP load
4. Conclusions
Acknowledgments
References