Fractal Study of Land Use Change in the Tailan River Basin, Xinjiang, China

Based on the land use data observed over the Tailan River Basin (TRB) during the years 1990, 2000, 2005 and 2008, fractal theory is adopted and applied to expound spatial distribution characteristics and variation law of land use change in the arid inland TRB, Xinjiang, China. The results demonstrate spatial fractal characteristics in all land use types. The analysis indicate that the fractal dimensions of different land use types in the TRB are in the order of waters > industrial, mining and residential areas > farmlands > grasslands > unused lands > woodlands in 1990, and in the order of waters > industrial, mining and residential areas > grasslands > farmlands > woodlands > unused lands in 2000, and in the order of waters > industrial, mining and residential areas > grasslands > woodlands > farmlands >unused lands in 2005, and in the order of waters > industrial, mining and residential areas > grasslands > unused lands > woodlands > farmlands in 2008. The fractal dimension values of land use in the TRB in 1990, 2000, 2005 and 2008 are calculated as 1.5993, 1.5986, 1.6079 and 1.6348 respectively. Fractal dimension of land use in the basin is decreased at first then increased, the spatial structure of land used exhibit complex trend, while the land use types show an increase trend. The stability indexes of spatial structure of land use in the TRB in 1990, 2000, 2005 and 2008 are 0.1720, 0.1563, 0.1435 and 0.1428 respectively. These values suggest that the stability of the spatial structure of land use in the basin is gradually decreased.

Diagnostic calibration of a hydrological model in an alpine area

Hydrological modeling depends on single- or multiple-objective strategies for parameter calibration using long time sequences of observed streamflow. Here, we demonstrate a diagnostic approach to the calibration of a hydrological model of an alpine area in which we partition the hydrograph based on the dominant runoff generation mechanism (groundwater baseflow, glacier melt, snowmelt, and direct runoff). The partitioning reflects the spatiotemporal variability in snowpack, glaciers, and temperature. Model parameters are grouped by runoff generation mechanism, and each group is calibrated separately via a stepwise approach. This strategy helps to reduce the problem of equifinality and, hence, model uncertainty. We demonstrate the method for the Tailan River basin (1324 km2) in the Tianshan Mountains of China with the help of a semi-distributed hydrological model (THREW).

Optimal Operation of Underground Reservoir in Tailan River Basin

Tailan river basin is a typical drought river basin in northwest China where construction of underground reservoirs is approved as an effective way to solve the problem of water resource shortage in the river basin. In order to ensure water supply efficiency of the underground reservoirs of the basin, it is necessary to research their recharge and supply patterns and to optimally operate them. This paper has, therefore, investigated different recharge locations and recharge ways through numerical simulation of underground flow in an underground reservoir area of the basin to explore a typical scheduling plan for optimal operation of the reservoir. The results show that it is better to recharge the reservoir using the flood season recharge approach at the centre of the reservoir area to ensure its continuous operation. Following from this recharge process, the use of a three-well pumping scheme is regarded as the best choice for optimal water supply from the reservoir. Also, the study indicates that for the same recharge amount, if the recharge time is closer to the pumping peak, then there is the more obvious effect of underground level recovery; the recovery is much better if the recharge time is more concentrated.