黄土区不同植被条件下的土壤抗冲性

该文以晋西黄土区刺槐林地、油松林地、农地、草地、道路边坡为研究对象,用野外实地放水冲刷的方法,以地表径流含沙量为指标,研究了不同植被条件下土壤的抗冲性,并就坡度、地被物、植物根系对土壤抗冲性的影响,以及流量和土壤抗冲性的相关性进行了探讨.研究得出不同植被条件下土壤的抗冲性为油松林地>刺槐林地>草地>道路边坡>农地.林草措施的抗冲效果与坡度密切相关,且随坡度的增大林草措施的防冲效果变小;地被物对土壤抗冲性有显著影响,没有地被物的土壤抗冲性明显小于有地被物的土壤;植物根系对土壤抗冲性的影响与冲刷水流的流量密切相关,冲刷水流的流量较小时根系对土壤抗冲性的改善效果更为突出.黄土区水土保持的关键是分散地表径流.

涟江流域不同类型河岸带模拟径流过程及氮流失研究

本研究以涟江流域作为研究对象,采用路线调查法对流域河岸带类型进行调查,根据土地利用方式、植被类型、地形地貌、土壤质地、人类活动强度、植被覆盖度等指标对涟江流域河岸带分类,选取不同类型河岸带运用径流槽模拟地表径流冲刷,测定土壤水分入渗和地表径流中氮流失量,以期能为流域面源污染防治以及良好河岸带结构的构建提供参考。研究表明:草地 + 壤土 + 山地、V型河谷 + 重度干扰类型河岸带地表径流产生量最大,单次冲刷最大地表径流量为757 mL;农业用地 + 水稻田撂荒地 +丘陵、U型沟谷 + 壤土 + 重度人类干扰类型与农业用地 + 坡耕地裸地 + 丘陵、U型沟谷 + 壤土 + 重度人类干扰类型产生量最低,6次冲刷均未产生地表径流。水分入渗量则相反,这三种类型单次冲刷入渗量分别为43 mL、800 mL、800 mL。不同类型河岸带模拟冲刷径流中总氮、铵态氮、硝态氮流失量均随冲刷次数增多而降低,其中硝态氮流失量大于铵态氮流失量。总氮、铵态氮、硝态氮流失量最大为建设用地 + 裸地 + 壤土 + 山地、V型河谷+重度干扰类型河岸带,流失量分别为4.60 mg/L、1.74 mg/L、2.11 mg/L;流失量最小为草地 + 壤土 + 山地、V型河谷 + 重度干扰类型河岸带,流失量分别为1.56 mg/L、0.45 mg/L、0.47 mg/L。本研究从局域尺度揭示了不同河岸带氮流失特征。

三峡库区紫色土坡地柑橘园不同耕作方式的水土流失研究

在重庆忠县坡度为11°的紫色土柑橘园,设中耕、覆盖、生草和清耕4种处理,用自动雨量记录仪记录降雨过程及降雨量,通过径流小区集水池测量不同耕作方式的地表径流量,取水样测定和统计地表径流中泥沙含量和流失量。结果表明:4种处理的地表径流量为清耕>生草>覆盖>中耕,相互处理间差异极显著,清耕年地表径流量分别比生草、覆盖和中耕高8.88%,10.79%和22.51%;处理间的地表径流水中的泥沙含量差异极显著,生草的泥沙含量分别比覆盖、清耕和中耕的低11.43%,38.00%和60.00%;不同耕作方式间的年泥沙流失量差异极显著,生草的泥沙流失量分别比覆盖、清耕和中耕的低10.84%,46.40%和58.99%。生草栽培可显著减少三峡库区坡地紫色土柑橘园的水土流失。

Influence of Vegetation Coverage on Surface Runoff and Soil Moisture in Rainy Season in Dry-hot Valley

[Objective]The research aimed to study the effects of vegetation coverage on the changes of soil moisture in rainy season in dry-hot valley.[Method]The surface runoff and soil moisture of slope with vegetation coverage and bare land in rainy reason in Jinsha River at Yuanmou County of Yunnan Province were observed continuously.Moreover,the statistical analysis was made based on the observation data.[Result]The vegetation coverage could decrease surface runoff and the surface runoff on bare land（CK） was 22 times as the plot with vegetation coverage.The soil water content in 0-180 cm layer with vegetation coverage increased by 37.8% than bare land.The stability of soil moisture content in deep layer was enhanced and the physical properties stability of soil was maintained.The soil moisture content in different depth of soil had significant difference and the changes of soil moisture content were obviously different.[Conclusion]The vegetation coverage of slope could change the soil hydrology obviously and keep soil moisture at the higher level,especially at soil layer below 20 cm.

Heavy Metal Runoff in Relation to Soil Characteristics

Cu, Zn, Pb and Hg runoff from yellow limestone soil and purple soils and the relationships between the mobility of the heavy metals and the soil characteristics were studied in laboratory using a rainfall simulator. The results showed that the concentrations of soluble Zn in surface runoff were significantly negatively correlated with the contents of <0.002 mm particles and CEC of the soils, indicating that Zn was mostly adsorbed by clays in the soils. The contents of Cu and Hg in surface runoff were positively related to their contents in the soils. The amounts of Cu, Zn, Pb and Hg removed by surface runoff were influenced by the amounts of soil and water losses and their contents in the soils, and were closely related to the contents of soil particles 1-0.02 mm in size.

Physical Effectiveness of Soil and Water Conservation Technologies in Drought Prone Areas of Western and Central Uganda

The effect of soil and water conservation （SWC） practices on controlling surface runoff and soil loss was studied in drought prone banana growing areas of Uganda, during the two major rainy seasons of 2014. The study was conducted at two sites-- Ntungamo （Southwest） and Sembabule （Central）, with comparable slopes of about 13%-25%. The treatments included mulch, manure, manure ＋ mulch and a control with no conservation. Results indicated that conservation practices of mulch and manure ＋ mulch significantly reduced surface runoff and soil loss by about 72%-85%, when compared to farmers＇ up-and-down cultivation practice （control）. It was also observed that significantly greater amounts of soil loss occurred from manure and control plots than the ones with mulch. Thus, the combination of manure and mulch is recommended for uptake by crop farmers in the study areas, if they are to overcome drought stress and adapt to changes in climate. More research is needed to quantify nutrient losses resulting from runoff under the different SWC techniques. Modeling such effects is essential in assessing the impacts of SWC practices on soil and crop productivity.

Infiltration Study for Urban Soil： Case Study of Sungai Kedah Ungauged Catchment

The DID （Department of Irrigation and Drainage） in Malaysia has produced a manual on urban stromwater management specifically for the Malaysia region with usage of infiltration method towards controlling the quantity and quality of surface runoff. With this method, the volume of surface runoff can be reduced and flood problems in major cities can be eliminated. The study areas of Sungai Kedah ungauged catchment are located at the northern region of Malaysia. The Kota Setar sub-catchment is located at the downstream of Sungai Kedah with the newly completed development of control barrage at the upper Kota Setar. This paper will describe the analyses of the infiltration curves at Kota Setar. The resulting infiltration maps have developed based on the infiltration capacities.

Spatial and Temporal Variability of Water Availability in the Yellow River Basin

The changes in hydrological processes in the Yellow River basin were simulated by using the Community Land Model(CLM,version 3.5),driven by historical climate data observed from 1951 to 2008.A comparison of modeled soil moisture and runoff with limited observations in the basin suggests a general drying trend in simulated soil moisture,runoff,and precipitation-evaporation balance(P-E) in most areas of the Yellow River basin during the observation period.Furthermore,annual soil moisture,runoff,and P-E averaged over the entire basin have declined by 3.3%,82.2%,and 32.1%,respectively.Significant drying trends in soil moisture appear in the upper and middle reaches of the basin,whereas a significant trend in declining surface runoff and P-E occurred in the middle reaches and the southeastern part of the upper reaches.The overall decreasing water availability is characterized by large spatial and temporal variability.

Linking vegetation cover patterns to hydrological responses using two process-based pattern indices at the plot scale

Vegetation cover pattern is one of the factors controlling hydrological processes. Spatially distributed models are the primary tools previously applied to document the effect of vegetation cover patterns on runoff and soil erosion. Models provide precise estimations of runoff and sediment yields for a given vegetation cover pattern. However, difficulties in parameterization and the problematic explanation of the causes of runoff and sedimentation rates variation weaken prediction capability of these models. Landscape pattern analysis employing pattern indices based on runoff and soil erosion mechanism provides new tools for finding a solution. In this study, the vegetation cover pattern was linked with runoff and soil erosion by two previously de- veloped pattern indices, which were modified in this study, the Directional Leakiness Index （DL[） and Flowlength. Although they use different formats, both indices involve connectivity of sources ,areas （interpatch bare areas）. The indices were revised by bringing in the functional heterogeneity of the plant cover types and the landscape position. Using both artificial and field verified vegetation cover maps, observed runoff and sediment production on experiment plots, we tested the indices＇ efficiency and compared the indices with their antecedents. The results illustrate that the modified indices are more effective in indicating runoff at the plot/hillslope scale than their antecedents. However, sediment export levels are not provided by the modified indices. This can be attributed to multi-factor interaction on the hydrological process, the feedback mechanism between the hydrological function of cover patterns and threshold phenomena in hydrological processes.