Coupled analysis on landscape pattern and hydrological processes in Yanhe watershed of China

Runoff erosion capacity has significant effects on the spatial distribution of soil erosion and soil losses. But few studies have been conducted to evaluate these effects in the Loess Plateau. In this study, an adjusted SWAT model was used to simulate the hydrological process of the Xihe River basin from 1993 to 2012. The spatial variabilities between runoff erosion capacity and underlying surface factors were analyzed by combining spatial gradient analysis and GWR (Geographically Weighted Regression) analysis. The results show that the spatial distribution of runoff erosion capacity in the studying area has the following characteristics: strong in the north, weak in the south, strong in the west, and weak in the east. Topographic factors are the dominant factors of runoff erosion in the upper reaches of the basin. Runoff erosion capacity becomes stronger with the increase of altitude and gradient. In the middle reaches area, the land with low vegetation coverage, as well as arable land, show strong runoff erosion ability. In the downstream areas, the runoff erosion capacity is weak because of better underlying surface conditions. Compared with topographic and vegetation factors, soil factors have less impact on runoff erosion. The red clay and mountain soil in this region have stronger runoff erosion capacities compared with other types of soils, with average runoff modulus of 1.79 × 10−3 m3/s·km2 and 1.68 × 10−3 m3/s·km2, respectively, and runoff erosion power of 0.48 × 10−4 m4/s·km2 and 0.34 × 10−4 m4/s·km2, respectively. The runoff erosion capacity of the alluvial soil is weak, with an average runoff modulus of 0.96 × 10−3 m3/s·km2 and average erosion power of 0.198 × 10−4 m4/s·km2. This study illustrates the spatial distribution characteristics and influencing factors of hydraulic erosion in the Xihe River Basin from the perspective of energy. It contributes to the purposeful utilization of water and soil resources in the Xihe River Basin and provides a theoretical support for controlling the soil erosion in the Hilly-gully region of the Loess Plateau.

Section: Swat Modelmentioning

confidence: 99%

Spatial Variabilities of Runoff Erosion and Different Underlying Surfaces in the Xihe River Basin

Wang

Yao

Liu

et al. 2019

“…However, along the gradient from outer suburban to urban, with increasing human disturbance, especially impervious surface, the original landscape pattern and underlying surface conditions will be modified. The scattered patches will lead to lower AI and higher SPLIT and PD values, and thus change flow regimes such as runoff directions and rates, and increase the annual runoff [58].…”

Section: The Impacts Of Landscape Indices On Water Balancementioning

confidence: 99%

WetSpass-Based Study of the Effects of Urbanization on the Water Balance Components at Regional and Quadrat Scales in Beijing, China

Zhang

Liu

Cheng

et al. 2017

Abstract:China is the largest country in terms of population and its booming urbanization has exerted negative effects on ground-surface hydrological processes at different spatial scales, land-use types, and water balance, such as surface runoff, groundwater recharge, and evapotranspiration. However, it is not yet well understood as to how the modifications of the spatial patterns of landscapes affect the water balance on a regional scale. In this study, the water and energy transfer among soil, plants, and atmosphere (WetSpass) model was applied to evaluate the urbanization effects on the water balance on a regional scale by using Beijing as the case city for this current study. The relationships among impervious surfaces, landscape pattern indices, and water balance components were also quantified. Results indicated built-up land in 2012 was 673 km 2 larger than it in 2000, mostly converted from croplands. WetSpass model also indicated the variation rates of annual average surface runoff, evapotranspiration and groundwater recharge were 7%, 0.4% and −2% in the whole Beijing area, while they reached 52%, 6% and −24% in the urban area of Beijing from 2000 to 2012, respectively. At a city scale, four districts-Dongcheng, Xicheng, Chaoyang, and Haidian-were characterized by higher impervious percentage, as reflected by lower groundwater recharge and higher surface runoff than other districts. At quadrat scale, however, groundwater recharge (surface runoff) was negatively (positively) correlated with impervious percentages. For landscape indices, the Aggregation Index was positively correlated with surface runoff and negatively correlated with groundwater recharge while Patch Density Index, Splitting Index, Patch Richness Density Index, and Shannon's Diversity Index presented opposite relationships. The results of this study can help to develop human knowledge about the impacts of urbanization on hydrological cycles on a regional scale.

“…Chen et al [8,26] established the location-weighted landscape contrast index (LCI) (see the methodology section for a thorough description of this method) to represent the ecological functions of landscape patterns based on the "source-sink" theory which has been commonly used to address the response of ecological process to landscape pattern changes [27,28]. Remarkably, the LCI is scale-independent (suitable for different sized watersheds) and regards not only the spatial configuration of the landscape but also the topographical characteristics of each land patch.…”

Section: Introductionmentioning

confidence: 99%

Responses of Sediment Yield to Vegetation Cover Changes in the Poyang Lake Drainage Area, China

Xiao

Yang

Cai

2016

Abstract:Ascertaining the relationships between sediment transport processes and vegetation cover is essential for watershed soil and water conservation. However, it is not easy to realize this target on a large scale. In this study, the location-weighted landscape contrast index (LCI) based on the "source-sink" theory of ecological processes was introduced to unravel the response of sediment yield to vegetation cover changes in the Poyang Lake drainage area (the largest freshwater lake in China). A modified location-weighted landscape contrast index (mLCI) was proposed to improve the accuracy and efficiency of the LCI. The average vegetation fraction of the study area significantly increased from 46.2% in Period I (1992Period I ( -1994 to 76.5% in Period II (2004)(2005)(2006) and then slightly decreased to 73.2% in Period III (2011. From Period I to Period II, the area-specific sediment yield (ASY) sharply decreased by 55%. In Period II, the "source" vegetation patches were found further away from the water bodies, and were more likely to be located on gentler slopes than in Period I. From Period II to Period III, the ASY sharply increased by 83%. In Period III, "source" patches were found closer to the water bodies than in Period II, whereas the "sink" patches were found further away from the water bodies. The high statistical correlation between LCIs/mLCIs and ASY indicated a sensitive response of the sediment yield to vegetation cover changes that significantly altered the sediment transport processes in the study area. The ASY was better correlated with the mLCI than with the LCI. Three key harnessing sub-watersheds of the Ganjiang watershed were identified by calculating the mLCIs: Qingfengshan, Yuanhe, and Jinjiang. This study supported watershed ecological management in the Poyang Lake drainage area and provided a methodology reference for future sediment transport process studies.