Research On Hydrological Responses To Land Cover And Meteorological Factors Change Based On SWAT Model In Beijiang Basin

As the second largest tributary of the Pearl River,Beijiang River basin is mainly distributed in the north region of Guangdong Province.As its ecological environment is fragile,the undertaking industrial transfer from Pearl River Delta region will definitely bring about a greater impact on the land cover, water quantity and water quality.As an important water source of Foshan and Guangzhou,Beijiang River plays an important role in flood control, irrigation and shipping social economy at the same time.It is important for the regional water balance and the rational development and utilization of water resources to study on land cover and climate change on the scale of basin,which can provide scientific and accurate data support for watershed management at the same time.This study successfully establishes the SWAT model of Beijiang River.The paper analyses the hydrological responses to land cover and climate change at the same time and then uses the CA-Markov model to forecast the change of land cover. The main research results are as follows:①Supported by GIS and the existing research results, both of the spatial database and attribute database of the SWAT model in Beijiang River basin are established. After the output data are calibrated and verified, SWAT model is proved to be suitable for the hilly area in the subtropical monsoon climate kike Beijiang River basin.②Between 2003 and 2008, evergreen forest, wetland went through a great drop in rate and area.Mixed forest and farmland increased by larger area; pasture, urban and built-up area of the area remained unchanged. There are 4 kinds of change types whose area is more than 2 000 km2, as follows:“evergreen forest�'mixed forest”>“pasture�'mixed forest”>“pasture�'agricultural land”>“mixed forest�'pasture”. The sub basins whose land cover change frequency is high are as follows:Binjiang, Wengjiang, Suijiang, Zhenjiang.All of these areas are low and flat, and near the economically developed Pearl River Delta region,which is proved that human activity has an obvious influence on the land cover change.③The central region of the Beijiang River Basin’s water resources is abundant, with a trend of decline to the rim, which is samely distributed with water yield and sediment yield.The center of precipitation is moving southward.The change of land cover and climate contributed to the change of runoff and the sediment load respectively accounted for 14.55%、10.81% and 82.27%、82.84%, so we can say that the change of Climate is the main factors of the change of runoff and the sediment load.④The water yield is positively correlated with the precipitation, while it is weakly negatively correlated with the average daily radiation.It can be concluded that the precipitation is the main factor of the change of water yield. The sediment load is weakly positively correlated with the precipitation, weakly negatively correlated with the daily average temperature and isn’t definitely correlated with the average daily radiation. Overall ranking of runoff capacity: wetland>agricultural land>pasture>mixed forest>evergreen forest, indicating that the Beijiang River basin woodland has a good effect on water conservation.Sediment production capacity ranking: mixed forest>pasture >evergreen woodland>agricultural land.⑤CA-Markov model is used to predicted the land cover changes in the Beijiang River basin.After verification with the true land cover of 2013, which shows that this model is suitable for large-scale study area to a certain degree.The average runoff and sediment load from 2016 to 2020 is increased by 0.15% and 6.2% compared with those of 2006 to 2010.