The Ecohydrology Response To Environmental Change At Lvergou Watershed In The Loess Plateau

The ecohydrology processes response to environmental change, is performance that the change of ecohydrology processes with the climate and land use changes. The Lvergou watershed has been taken as study area, through analyzing the climate, land use and soil datas, forecasting climate and land use change the next 40 years. The improved eco-hydrological model TOPOG was adopted to simulate the ecohydrology processes, and analyze the causes of its. The research provided the technical support for the department of soil and water conservation and land use. The main conclusions were as follows:(1) The rainfall has large fluctuations between years, with average rainfall of 533.65mm. The sudden change did not occur throughout the study period, but has been in obvious decline. The rainfall in June-September accounted for 85.62% in years. For many years, the average annual precipitation on upper> middle> lower reaches of the property, besides increasing with altitude and the more the precipitation, the more spatial heterogeneity. In the past 50 years, the high, average and minimum temperatures increased at the speed of 0.024℃/a,0.0279℃/a and 0.0289℃/a, and the sudden change occurred at 1997-1999. The actual evapotranspiration has no significant of sudden change, and been in decline mainly affected by precipitation. The potential evapotranspiration increased, and decision of precipitation and temperature change. Climate in next 40 years has been predicted, based on analyzing of climate change.(2) The land use/cover has great changes at Lvergou watershed in the Loess Plateau during the study period. The mainly changes is the area of grassland and sloping land were reduce, terraces and woodland area were increase. In 1986-1995 for the overall planning of land use, the type and area of land use violently changes; in 1995-2001 for the self-adjustment period, the number of small-range changes; in 2001-2008 was stable, a variety of land use change slightly. Appling CA-Markov model, using IDRISI software, removing the acceleration of land use change, based on the rate of land use change, the quantity and spatial of land use has been simulated in forecast at study watershed.(3) The relationship between hydrologic and physical of soil in Lvergou watershed is closely. There are different particle composition and capillary, in different types of land use soil. But soil moisture changed slightly the vertical direction. The soil permeability coefficients of locust forest is biggest, the cultivated land and orchard is smallest. The soil permeability coefficient is well related to bulk density and non-capillary pore. The anti-erodibility (k) changes in a small bound. The largest, the least k appeared in grassland and slope farmland. The k precipitated on upstream grass> terrace> orchard> slope farmland. The C and plant roots are significantly relevant, and keep decreasing with the increase of slope.(4) The precipitation and sediment changed in a same way between the annual, during 1982-2010 in Lvergou watershed. Sediment is response for runoff strongly. Runoff and sediment have changes in based period, non-significant change period and significant change period. During the non-significant change period and significant change period, the contribution rate of land use reduced, and the contribution rate of climate increased, control Measures is important to decline runoff and sediment.(5) Wetness index(WI) varies as a consequence of these different data inputs. WI increased by uniform drainage flux value(q) increase; A comparison was made between a set of uniform transmissivity (T) and uniform rainfall (R) values, and found that TOPOG predicted the expected trend that soil moisture within the watershed increased with increasing uniform T and uniform R values. In different seasons, the value of radiation-weighted WI is summer>equinox> winter. Erosion hazard index of watershed (HW) is lower with the best land cover, and greater with high rate of surface exposed. In the same ground cover, soil erosion occurs mainly on the slope, and channel erosion is weak in the study area. The rainfall at the range of 10-50mm/d caused a wind range of area to landslide in Lvergou watershed. The landslide hazard index (Rcr) in upslope and upstream were lower. The probability of occurrence of landslide at groove was the smallest in the same case of rainfall. The improved model enhanced the Nash efficiency coefficient from 0.68 to 0.81 in runoff processes, and from 0.72 to 0.85 in sediment transport processes, the simulated values were more in line with the observed values.(6) The improved TOPOG model was adopted to simulate and analysis the ecohydrology processes based on the climate and land use forecasted in next 40 years. The precipitation, runoff and sediment will gradually reduced, showed seasonal variation. The evapotranspiration gradually increased the proportion, the proportion of runoff gradually decreased of total water resources in the future. The contribution rate of land use change on runoff and sediment will gradually decrease, and the contribution rate of climate change will be more and more significant. The contribution rate of climate change on runoff will be larger than contribution of sediment, while the contribution rate of land use change on sediment will be larger than contribution of runoff. The correlation between climate change, land use changes and ecohydrology processes is going to enhance in the rainy seasons. The coefficient of hydrological processes and climate is greater than land use change, more, obviously in the rainy seasons.