[Background] Climate variations, especially the changes of precipitation are considered as a main factor of runoff decrease. However, previous studies reported that the feedback of runoff to the precipitation varied in different are as and time periods. It might be also influenced by the basins'scales. This work is to reveal the relationship between runoff and precipitation in different spatial-temporal scales in Chaobaihe Basin, the major water resource area for Beijing, from 1957 to 2001. [Methods] The climate data was from meteorological stations of China Meteorological Administration while the runoff data was from hydrological stations of Chaobaihe Basin. The precipitation series of each sub-basin were calculated by Thiessen polygon method, and Mann-Kendall trend test was used to identify the change trends and abrupt change points. At last, the relationship between precipitation-runoff were analyzed using regression analysis. [Results] The runoff change trend in each sub-basin was lightly different from each other,differing in the extent of fluctuations and degree of stability, however, the difference was not significant. According to the analysis of abrupt change points, the 44 years was divided into 3 periods:runoff increase period, decline period and stable period. The results suggested that the runoff decreased sharply from 1960 to 1970 and after 1990 the runoff increased slightly, while from 1970 to 1990,the runoff fluctuated greatly and did not show obvious rules. On the otherhand,based on the Pearson correlation coefficient from regression analysis between precipitation and runoff,the value became smaller as the sub-basin scale in creased. This meant that precipitation affected the small basins more significantly, and the affecting factors in the large basins were more complex. The larger the basin area was,the weaker the correlation between runoff and precipitation was. In addition, the relations also showed differences indifferent period. The Pearson correlation coefficients in increase and stable period were larger than that in the decrease period. This difference indicated that the responses of runoff to the precipitation in increase and stable period were much stronger than indecline period. Increase of runoff was deeply influenced by precipitation while the decrease of runoff was affected more by other factors. [Conclusions] Human activities and climate changes are two factors that influence the runoff. In Chaobaihe Basin and its sub-basins, increasing precipitation leads to the increase of runoff while human activities should be responsible for the runoff decreasing. Besides,in small-scale basins, precipitation variation could explain the change of runoff verywell, however in large-scale basins, human activities might be the main reason causing the changes of runoff. Thus, in order to guarantee the water yield, management of human activities such as optimization the land use and reasonable utilization of water resources is crucially important.

[Background] Gangue is an undesirable material generated during shaft building, coal mining, and coa lwashing. Gangue is dug out from under ground and piled up on the surface, which is called gangue dump. Because of the harsh site conditions of gangue dump, the recolonization of plants is very difficult. [Methods] In order to prevent erosion and facilitate revegetation in coal gangue dump, the volumetric water content and runoff of a coal gangue slope under natural precipitation were monitored for 2 years. The coal gangue was evenly spread on the 38° runoff plot and formed a slope with a depth of 70 cm. The base of the slope was impermeable,and the surface and groundwater runoffs were collected separately1 day after each rainfall event. The effects of natural precipitation and weathering on volumetric water content and runoff were tested. [Results] 1) On average, during each light rainfall event(<10mm/d), 0.014 mm surface runoff and 0.019 mm groundwater runoff were produced,i.e., the amounts of surface and groundwater runoffs were similar, and a small amount of surface and groundwater runoffs were generated on coal gangue slope. Moderate rains happened at the highest frequency and accounted for most surface runoff. In each moderate rainfall event (10-25mm/d),0.117 mm surface runoff and 0.962 mm groundwater runoff were generated, meaning that more precipitation was discharged as ground water runoff. While heavy rains occurred at the lowest frequency and accounted for most groundwater and total runoff, during each heavy rainfall event(>25mm/d), 0.254 mm surface runoff and 4.253 mm groundwater runoff were generated. 2) The amount of surface runoff was positively correlated to precipitation, and the amount of groundwater runoff was positively correlated to maximum precipitation intensity and mean precipitation intensity. However,the correlation between precipitation intensity and surface runoff was not significant, which probably resulted from the fact that the infiltration rate of coal gangue was generally higher than the precipitation intensity. The correlation between precipitation and ground waterrunoff was also not significant. 3) In 2014,due to the increase of weathering, the amounts of surface runoff, ground water runoff and total runoff during each light rainfall event decreased by 50%, 100% and 80% respectively, compared to 2013. During moderate rainfalls, they decreased by 88%, 82% and 97% respectively. 4) Coal gangue held a certain amount of water, and the volumetric water content in 20-30 cm coal gangue was the most. Volumetric water content in 10-30 cm ones increased as gangue weathered despite less water input from precipitation in 2014, indicating water holding capacity increased. Even though gangue in 10 cm was highly weathered, the water content was low because of high evaporation rate. 5) Because of its coarse texture and high in filtration capacity, the surface runoffs on the coal gangue slope during light, moderate and heavy rainfall events were 4%, 26% and 19% of those on the soil slope respectively. [Conclusion] This research will guide the practice of soil and watter conservation in gangue dump.

[Background] Well-managing the current status of soil erosion and the achievements of prevention, are the purposes of dynamic monitoring and evaluation of regional soil and water loss. The methods of dynamic monitoring and evaluation of regional soil and water loss in China can be divided into five categories as following: qualitative analysis method, sampling statistical analysis method, the method based on composite index, the method based on geostatistical analysis and remote sensing monitoring, and the method based on distributed models. All these methods require tremendous amount of basic data and the support of big data technique. While the big data is built up andanalyzed sufficiently, the data resources can be fully mined,and the scientificity, integrity and timeliness of the dynamic monitoring can be improved significantly. [Methods] The big data for dynamic monitoring and evaluation of regional soil and waterloss are consisted of basic and static data, dynamic and updated data, and analysis and evaluation data. Most of these data, beside monitoring and observation of soil and water conservation, can be collected and mined from water resources and hydrology big data, territorial resources big data, meteorology big data, forestry and agriculture big data and soon. Dynamic monitoring and evaluation based on big data can be achieved by collecting and mining data, building data assembles of dynamic monitoring and evaluation of regional soil and waterloss, and utilizing the calculation platform of cloud-based network. [Results] In the near term, the top-level design should be improved: to build the centers of big data, to implement the integration and sharing of big data, to promote the standardization of data, to innovate the mode of big data and cloud network services, to improve the information collection from monitoring network and infrastructure construction of data network, and finally to explore and improve the methods of regional soil and waterloss dynamic monitoring and evaluation based on big data. [Conclusions] We should promote big data co-ordination on national, industry and regional levels gradually, unify the big data standards ;and then utilize the existing resources of big data sufficiently such as water resources and hydrology big data, territorial resources big data, meteorology big data, forestry and agriculture big data and soon. We also should establish the management, application and sharing platform of big data, use the administrative and economic measures—accompanied by the necessary basic research and the construction of professional teams—so as to jointly promote the application of big data in the fields of regional soil erosion monitoring and evaluation and soil and water conservation industry,and to assist governmental decision-making for economic and social development.

The JialingRiver Basin is one of the important sources of runoff and sediment in the upper reaches of the Yangtze River Basin. Investigation on the mechanism of the influence of climate and underlying surface conditions on runoff and sediment discharge reveal the reason for the change of runoff and sediment discharge in JialingRiver Basin in recent decades,therefore,analyzing the influence contribution rates from 2 factors of climate and underlying surface conditions on the changes of runoff and sediment has the important significance in the JialingRiver Basin,and it also can be used as certain significant guidance to control the basin sediment variability of soil and water conservation work. [Methods]SWAT model was adopted tos imulate the process of runoff and sediment in the JialingRiver Basin since 1975, and was calibrated by processing the basic data (including landuse, DEM, soil data and meteorological data) and using these diment data of the hydrologic stations,furthermore the driving factors resulting in the changes of runoff and sediment as well as their contribution rates to the changes of runoffand sediment were analyzed by the method of model control variables. [Results] The study showed that:during the 23 years from 1988 to 2010,1) the total runoff in Jialing River Basin was 3.59% less than the average runoff, and the total amount of sediment decreased by 5.14% and only resulted from the change of climate condition. The contribution rate of climate changes on the decrease of runoff was 23.81% and on the decrease of sediment was 8.2%. 2) Compared with the average total amount of runoff and sediment discharge,the total runoff in JialingRiver Basin had been a decrease of 171.854 billion cubic meters and the sediment discharge had been a decrease of 1462 million tons. The contribution rate of underlying surface changes on the decrease of runoff was 76.19% and on the decrease of sediment was 91.8%. [Conclusions] 1) The influence of weather change on runoff and sediment in JialingRiver Basin isl ittle. 2) The changes of runoff and sediment in JialingRiver Basin are mainly caused by the changes of underlying surface conditions. Although this paper shows the underlying surface is the main reason on the change of runoff and sediment in JialingRiver Basin, by the model precision it is in feasible to accurately distinguish the contribution rate of varied driving factors of underlying surface to the change processes of runoff and sediment. The underlying surface factors include soil and water conservation measures, land use change, reservoir hydro power station and the construction of large water conservancy facilities, and their influences on the runoff and sediment need further studying.

[Background] In order to study the impacts of different vegetation types in Badaling area on the soil anti-erodibility and further reveal the soil anti-erodibility under different vegetation types, researches were conducted on 4 forest stands of Pinus tabuliformis, mixed conifer and broadleaf, broadleaf and shrub. [Methods] Based on the data from adequate field investigation as well as sampling and laboratory analysis, principal components analysis (PCA) along with relevant analytical methods were adopted in the study. [Results] After dry sieving, the particle size of aggregates in Badaling rea was mostly found in 5 - 2 mm and the least in 0.5 - 0.25 mm. By contrast, after wet sieving, most aggregates were in small particle size ( <0.25 mm) while large-size (10 -5 mm) aggregates accounted for he smallest proportion. The geometric mean diameter (GMD), mean weight diameter (MWD), percentage of aggregate destruction (PAD) as well as the content of soil water-stable aggregate (WSA)> 0.25 mm of P. tabuliformis forest, mixed conifer and broadleaf forest and shrub forest all showed that aggregates in 10 -20 cm layer of the forest land were the most stable, while in 0 -10 cm layer they were in the worst stability, however this was not applied to broadleaf forest. To make better comparisons about the capacity of soil anti-erodibility in the 4 types of forestland, 12 indexes were defined, including the physical and chemical features of soil and aggregate characteristics. And based on the method of PCA,the best and most suitable index system was established for evaluating the soil anti-erodibility in Badaling area. Among all the indexes, the GMD of dry-sieved soil was then selected via analysis as the best one to describe the soil anti-erodibility of the different typical forestland. Analytically, in Badaling area, the topsoil (0 -10 cm) of broadleaf forest showed the greatest resistance to soil erosion, followed by shrub forest, mixed conifer and broadleaf forest and P. tabulifomis forest. Analysis also showed the anti-erodibility of 0 - 20 cm layer, where erosion was most likely to take place, with the figures for the different types of vegetation, was shrub forest > P. tabulifomis forest > broadleaf forest > mixed conifer and broadleaf forest. Synthetically, considering the average conditions for each layer, the final result of the soil evaluation was presented in the form of comprehensive soil anti-erodibility index. And the comprehensive soil anti-erodibility of the 4 types of forestland was shrub forest > P. tabulifomis forest >mixed conifer and broadleaf forest > broadleaf forest. [ Conclusions ] The result has practical significance to the scientific evaluation of the soil and water conservation function of the different forest stand in the research area. Meanwhile, the results of the study has certain reference value for both egional soil and water conservation and the further study on the mechanism of soil erosion. Therefore,he research may contribute to the prevention and control of regional soil and water loss and the coordination of regional land use.

[Background] The fragile ecosystem in the Losses Plateau is facing the crisis of degradation at present, which seriously impede the development of local economy. Agroforestry system which can restore the ecological balance, reduce the soil and water loss amount thus increase the economic income has become the main agricultural practice recently in losses region of west Shanxi province. However, the unreasonable management for irrigation and fertilization in agroforestry system may also increase the interspecific competition, which may cause the reduction of yields even the occurrence of soil erosion. Therefore, it is essential to find a more effective and economical irrigation and fertilization method in agroforestry of this area to ease the interspecific competition and conserve both the moisture and soil. [Methods] An experiment of water and fertilizer coupling with 2 factors (irrigation and fertilizer) and 3 application rate levels was carried out in a typical apple*maize intercropping system in the loess region of Shanxi Province. The effect of different irrigation and fertilization regimes on soil moisture especially the spatial and temporal distribution at filling and maturing stage of maize were analyzed. There were 9 treatments in the study based on the irrigation and fertilization coupling (W₁F₁, W₂F₁,W₃F₁, W₁F₂, W₂ F₂, W₃F₂, W₁F₃, W₂F₃, and W₃F₃). The regimes were designed based on 3 irrigation levels: a) Low, (W1), 50% Fc (field capacity); b) Medium, (W₂), 65% Fc; and c) High, (W3), 85% Fc. The fertilizer levels were: F1, (N (289 kg/ ha) + P₂O₅(118 kg/ ha) + K₂O (118 kg/ ha));F₂ (N (412.4 kg/ ha) + P₂O₅ (168.8 kg/ ha) + K₂O (168.8 kg/ ha)); F₃(N (537 kg/ ha) + P₂O₅ (219 kg/ ha) +K₂ O (219 kg/ ha)); and CK (no irrigation and fertilization throughout the growth season). All irrigation and fertilizer application amount were set up based on the water and nutrients requirements for maize and apple trees in this area. [Results] The application of irrigation and fertilization enhanced soil moisture by 7.6% than CK at filling stage, and 10.9% at maturing stage. The maximum soil moisture achieved in W3F1 treatment at filling stage. There was no significant difference in soil moisture along the distances from the tree line to maize in the plot, suggesting that the reasonable irrigation and rtilization alleviated the soil water competition between different species in intercropping system. Moreover, the soil moisture decreased firstly with the increase of soil depth within 0 - 30 cm depth and then increased whereas the trend maintained constantly the soil moisture decreased with the increase of soil depth (0 - 60 cm) in CK. Accordingly, the application of water and fertilizer increased the soil moisture in deep soil layer (30 -60 cm) significantly at maturing stage. [Conclusions] According to the results in jointing-filling stage, the soil moisture (0 -60 cm) was optimal when the total irrigation and fertilizer amount were 1 300 m³ / ha and 525 kg/ ha, respectively. Consequently, the results of this study may provide theoretical basis and technical support for the local farmers to manage water and fertilizer in a more effective way for intercropping system in the loess region of western Shanxi Province.

[Background] An unreasonable land use structure causes severe soil erosion and increases runoff-sediment yield or even major environment problems, especially brings huge negative effects on ecologically fragile arid and semiarid area. The objectives of this study were to model the effects of the changes of land use structure on reducing runoff-sediment yield in the Luoyugou watershed, a typical case of gully region of the Loess Plateau. [Methods] The Soil and Water Assessment Tool (SWAT) was used to model daily runoff and sediment data from this basin collected from 1986 to 2000. First, the model was used to determine acceptable values of the P-factor, R-factor, coefficient of determination (R²), and the Nash-Sutcliffe coefficient (E_ns) during both the calibration and validation periods. Then, the model was used to determine which kind of major land use in Luoyugou watershed can be chosen with the least runoff and sediment yield. Next, the land use structure of Luoyugou Watershed were adjusted to six types, and the model was used to simulate the six scenarios with 1986—2000 meteorological data of this basin. [Results] 1) Compared with those in 1995, the effect on reducing runoff and sediment yield of forest and terraced fields were better than the grassland and slope farmlands. Under extreme scenario simulation, runoff under forest and terraced fields decreased about 56.86% and 11.97% respectively, while the sediment decreased about 80% of corresponding runoff-sediment yield in 1995. 2) The runoff-sediment yield was influenced by the concentration of forest land. Compared with the low concentration of forest, runoff amount and sediment under high concentrated forest decreased at most of 4% and 27% respectively. However, there was probably a threshold of concentration, and if the concentration degree was greater than the threshold value, the watershed runoff-sediment yield was almost invariable, but it remains to be further validated. 3) The runoff and sediment yield under various land use types with the same area proportion were related to their distributive location. Different structures resulted in varying reduction of sediment yield and almost undifferentiated runoff. The sediment yield in the drainage of the watershed reduced in a varied level in 1995, and maximum reduced proportion of sediment yield was 26.79%. Moreover, when forest land locates in upstream, runoff-sediment yield at upstream and midstream were the least. [Conclusions] Therefore, concentration degree of forest should be more considered in adjusting the land use structure. More attention should be paid to optimize the land use structure of upstream especially the source of the watershed. Vegetation measures should be implemented in the source areas producing runoff and sediment, and the terraced fields should be placed in the midstream and downstream as much as possible.