This paper analyzed the water-retention mechanism of feldspathic sandstone(fine-(<1 mm diam.)and gravel-sized(2-3 cm diam.)in Mu Us Sandy Land,Northwest China.The objective of this study is to study the effect of feldspathic sandstone amendment on water retention in sandy land.The results showed that as the proportion of fine feldspathic sandstone in the sandy land soil increased,the soil texture changed from sand to silt loam,the capillary porosity gradually increased from 26.3%to 44.9%,and the soil saturated hydraulic conductivity decreased from 7.10 mm/min to 0.07 mm/min.Feldspathic sandstone gravel formed micro-reservoirs in the sandy land soil,playing the role of a′water absorbent′and′water retaining agent′in sandy land.Amendment with feldspathic sandstone can increase water retention in the arable layer of sandy land by 67%.This study provides a theoretical basis for the amelioration of sandy land on a large scale.It can be concluded that amendment with feldspathic sandstone can improve the physical properties of sandy land soil and increase soil water retention.
To study the groundwater dynamic in the typical region of Sanjiang Plain, long-term groundwater level observation data in the Honghe State Farm were collected and analyzed in this paper. The seasonal and long-term groundwater dynamic was explored. From 1996 to 2008, groundwater level kept declining due to intensive exploitation of groundwater resources for rice irrigation. A decline of nearly 5 m was found for almost all the monitoring wells. A time-series method was established to model the groundwater dynamic. Modeled results by time-series model showed that the groundwater level in this region would keep declining according to the current exploitation intensity. A total dropdown of 1.07 m would occur from 2009 to 2012. Time-series model can be used to model and forecast the groundwater dynamic with high accuracy. Measures including control on groundwater exploitation amount and application of water saving irrigation technique should be taken to prevent the continuing declining of groundwater in the Sanjiang Plain.
Different types of vegetation occupy different geomorphology and water gradient environments in the San-jiang Plain,indicating that the soil moisture dynamics and water balance patterns of the different vegetation communi-ties might differ from each other.In this paper,a lowland system,perpendicular to the Nongjiang River in the Honghe National Nature Reserve(HNNR),was selected as the study area.The area was occupied by the non-wetland plant forest and the typical wetland plant meadow.The Microsoft Windows-based finite element analysis software package for simulating water,heat,and solute transport in variably saturated porous media(HYDRUS),which can quantita-tively simulate water,heat,and/or solute movement in variably-saturated porous media,was used to simulate soil moisture dynamics in the root zone(20-40 cm) of those two plant communities during the growing season in 2005.The simulation results for soil moisture were in a good agreement with measured data,with the coefficient of determi-nation(R2) of 0.44-0.69 and root mean square error(RMSE) ranging between 0.0291 cm3/cm3 and 0.0457 cm3/cm3,and index of agreement(d) being from 0.612 to 0.968.During the study period,the volumetric soil moisture content of meadow increased with the depth and its coefficient of variation decreased with the depth(from 20 cm to 40 cm),while under the forest the soil moisture content at different depths varied irregularly.The calculated result of water budget showed that the water budget deficit of the meadow was higher than that of the forest,suggesting that the meadow is more likely to suffer from water stress than the forest.The quantitative simulation by HYDRUS in this study did not take surface runoff and plant growth processes into account.Improved root water uptake and surface runoff models will be needed for higher accuracy in further researches.
LI ShanghuaZHOU DeminLUAN ZhaoqingPAN YunJIAO Cuicui
三江平原位于中国东北部,是国家重要的商品粮基地,水资源的变化影响区域农业经济的发展。应用SWAT(Soil and Water Assessment Tool)模型模拟挠力河上游流域径流变化特征,为研究沼泽性河流水文变化特征提供有效的方法。根据水文相似性原理和参数移植法把校准的模型应用于七星河流域,进行无资料流域的径流模拟,年径流模拟校准期和验证期的Nash-Sutcliffe效率系数、相关系数R2、相对误差PBIAS值分别为0.84、0.94、-5.70和0.91、0.93、-6.46,表明SWAT模型可以应用到七星河流域。
