Spatial Pattern Of Soil Salinization In The Lower Reaches Of The Plain Reservoirs In Arid Area

Water resources are a basic resource to support the development of social economy in arid area. Due to the oasis area climate is very dry all the year round,water resources are very scarce and in the spatial and temporal distribution is very uneven, greatly limits the development of local oasis agriculture. To provide enough water for the growth of crops, many state in Xinjiang in the plains built the size of the reservoir. Reservoir construction on the one hand, to ease the pressure on the local agricultural water and promote the development of agricultural economy; on the other hand, with the reservoir volume increases and the problem of reservoir leakage caused by various factors, water level of groundwater in the downstream regions of the substantial uplift. Because of the strong evapotranspiration effects, large number of subsoil and groundwater salinity is concentrated in the soil surface, which forming a land salinization phenomenon. Land salinization not only destroys the surface vegetation, but also affects the growth of crops. And it accelerates the process of soil degradation, which threatens the balance of the local oasis ecosystem. In this study, the territory of Fukang City Liuchengzi Reservoir was taking as the research target. In view of the impacts of plain reservoir on the soil salinization of the downstream area, using the combination of Geo-statistical and 3S technology to study and analysis the temporal and spatial distribution characteristics of saline soil spectra and the spatial differentiation characteristics of the soil salinity at different depths in the downstream area of Liuchengzi reservoir. So as to reveal the regional spatial variation regularity of soil salt, and provide theoretical reference for the management of local soil salinization. Specific research conclusions are as follows:1. From the time point of view, in the downstream of reservoir the mean value of soil salinity index SI1 and the CV value is showing a trend of increasing year by year from 2002 to 2013, indicating that the degree of soil salinization is deepening, and the difference of soil salinization is increasing gradually. From the point of space, therange of 0 to 2400 meters around the reservoir, SI1 generally presents the characteristics of increasing year by year. Among them, in the range of 1200 m to2400 m, SI1 have a fluctuation, and its specific performance is the trend of increasing first and then decreasing. However, the data for each year are similar, that is to say within this scope the soil salinization in each year is similar, and the effect of reservoir on soil salinization is decrease with the increase of distance.2. 2007, 2002 and 2013, the spatial structure of soil salt index has a strong spatial correlation, and the total spatial variability decreases gradually, and the spatial autocorrelation distance increases year by year. This reflects that the variation is mainly caused by the inherent regional factors of the groundwater.3. Compared with 2002, in 2007 the area of severe salinization solonchak has increased, but mild, moderate salinization area reduce is showing a downward trend.In 2013, mild, moderate and severe salinization area is further reducing. Saline soil area increased substantially, and it is 2.28 times of 2007. Salinization degree is becoming more serious.4. The average soil salt content in the lower reaches of Liuchengzi reservoir is in the normal distribution, and the variation coefficient is between 0.67 and 0.44, which belongs to the medium variation intensity; Soil salt content from the surface to the bottom gradually decreased. In addition, The spatial correlation distance of soil salinity increased gradually with the increase of soil depth, the Co/Sill of soil salinity content is 3.05% ~ 5.44%, which with significant spatial correlation.5. The serious soil salinization area is mainly distributed near the dam. With the increase of distance with the reservoir dam, the degree of soil salinization becomes lighter. In the vertical direction, the change of the degree of soil salinization showed the trend of decreasing with the deepening of the soil depth, while the area of the saline soil decreased gradually.