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261.
Rain gardens are infiltration systems that provide volume and water quality control, recharge enhancement, as well as landscape, ecological, and economic benefits. A model for application to rain gardens based on Richards equation coupled to a surface water balance was developed, using a two-dimensional finite-volume code. It allows for alternating upper boundary conditions, including ponding and overflow, and can simulate heterogeneous soil-layering or more complex geometries to estimate infiltration and recharge. The algorithm is conservative, and exhibits good performance compared to standard models for several test cases (less than 0.1% absolute mass balance error); simulations were also performed for an experimental rain garden and comparisons to collected data are presented. The model accurately simulated the matrix flow, soil water distribution, as well as deep percolation (potential recharge) for a natural rainfall event in the controlled experimental setup. 相似文献
262.
密云水库水文特性分析 总被引:2,自引:0,他引:2
采用密云水库自建库至2005年的资料,利用水文统计分析方法,分析了密云水库径流、泥沙、降水、蒸发等水文特征的变化规律,为合理利用密云水库水资源提供了依据. 相似文献
263.
Del Prado A Misselbrook T Chadwick D Hopkins A Dewhurst RJ Davison P Butler A Schröder J Scholefield D 《The Science of the total environment》2011,409(19):3993-4009
Multiple demands are placed on farming systems today. Society, national legislation and market forces seek what could be seen as conflicting outcomes from our agricultural systems, e.g. food quality, affordable prices, a healthy environmental, consideration of animal welfare, biodiversity etc., Many of these demands, or desirable outcomes, are interrelated, so reaching one goal may often compromise another and, importantly, pose a risk to the economic viability of the farm.SIMSDAIRY, a farm-scale model, was used to explore this complexity for dairy farm systems. SIMSDAIRY integrates existing approaches to simulate the effect of interactions between farm management, climate and soil characteristics on losses of nitrogen, phosphorus and carbon. The effects on farm profitability and attributes of biodiversity, milk quality, soil quality and animal welfare are also included. SIMSDAIRY can also be used to optimise fertiliser N.In this paper we discuss some limitations and strengths of using SIMSDAIRY compared to other modelling approaches and propose some potential improvements. Using the model we evaluated the sustainability of organic dairy systems compared with conventional dairy farms under non-optimised and optimised fertiliser N use. Model outputs showed for example, that organic dairy systems based on grass-clover swards and maize silage resulted in much smaller total GHG emissions per l of milk and slightly smaller losses of NO3 leaching and NOx emissions per l of milk compared with the grassland/maize-based conventional systems. These differences were essentially because the conventional systems rely on indirect energy use for ‘fixing’ N compared with biological N fixation for the organic systems. SIMSDAIRY runs also showed some other potential benefits from the organic systems compared with conventional systems in terms of financial performance and soil quality and biodiversity scores. Optimisation of fertiliser N timings and rates showed a considerable scope to reduce the (GHG emissions per l milk too). 相似文献
264.
Impacts of rainfall events on runoff water quality in an agricultural environment in temperate areas 总被引:2,自引:0,他引:2
Since a rise in dissolved organic carbon (DOC) concentrations has been observed for surface waters at least over the last two decades, a change in weather conditions (temperature and precipitations) has been proposed to partly explain this increase. While the majority of DOC delivery from soils to stream occurs during rainfall events, a better understanding of the rainfall influence on DOC release is needed. This study has been conducted in Brittany, western France, on agricultural experimental plots receiving either cattle manure (CM) or pig slurry (PS) as fertilizers in accordance with local practices. Each plot was instrumented with a flow meter and an auto sampler for runoff measurements. The results show that export of DOC during high intensity events is higher than during lower intensity rainfalls. Fertilization has a noticeable impact on total organic carbon (TOC) fluxes with an increase of five to seven folds for PS and CM respectively. If TOC shock load occurs shortly after the rainfall peak, DOC maximum appears with the first flush of the event. Organic carbon (OC) is mainly under colloidal (41.2%) and soluble (23.9%) forms during the first stage of a rainfall event and a control of rainfall intensity on OC colloidal transport is suggested. These findings highlight the potential risk of receiving water quality degradation due to the increase of heavier rainfall events with climate change in temperate areas. 相似文献
265.
Numerical Analysis of Rainfall Effects on Slope Stability 总被引:7,自引:0,他引:7
The finite element analysis of transient water flow through unsaturated–saturated soils was used to investigate effects of hydraulic characteristics, initial relative degree of saturation, methods to consider boundary condition, and rainfall intensity and duration on water pressure in slopes. The finite element method with shear strength reduction technique was used to evaluate the stability of slopes under rainfall. The results of the finite element analysis indicated that the hydraulic characteristics, initial relative degree of saturation, methods to consider boundary condition, and rainfall intensity and duration had significant influence on the water pressure in slopes, and thus on the stability of slopes under rainfall. The good comparisons of the numerical results with statistical and observational results showed the ability of the finite element analysis to evaluate the stability of slopes under rainfall. 相似文献
266.
为了使TOPMODEL模型结构更合理,并能够用于半湿润地区或半干旱地区的径流过程模拟,文章对TOPMODEL模型的蒸发产流模块以及汇流模块进行改进,在蒸发产流模块中添加植被冠层截留蒸散发模型和Holtan超渗产流模型,汇流模块中坡面汇流采用瞬时单位线模型,河道汇流采用马斯京根河道洪水演进模型。通过对半湿润地区流域内降雨径流过程的模拟验证,表明通过对TOPMODEL模型的改进,模型对半湿润地区的降雨径流过程模拟精度有很大的提高,拓展了TOPMODEL模型适用范围。 相似文献
267.
To improve the accuracy of hydrological simulations in the groundwater overexploitation zone of North China, it is necessary to study the characteristics of shallow aquifer recharge on daily scale. Three shallow aquifer recharge indices were used to quantify shallow aquifer recharge in two ways. The recharge coefficient was used to quantify the amount of shallow aquifer recharge. The recharge duration and water table rise coefficient were used to quantify the recharge temporal process. The Spearman rank correlation coefficient and regression analysis were used to determine the relationships between aquifer water table depth (WTD), rainfall, and shallow aquifer recharge. The Jiangjiang River Basin, a tributary of the Haihe River, was selected as the study area. The results showed that the recharge coefficient first increased, then decreased, and finally leveled off as WTD increased. When WTD was between 5 and 6 m, the recharge coefficient reached its maximum (approximately 0.3). When WTD was greater than 10 m, the recharge coefficient remained stable (around 0.12). With regard to the sources and forms of recharge, preferential flow was dominant in the areas near the extraction wells. In contrast, plug flow became dominant in the areas distant from the wells. With the reduction of rainfall duration, the proportion of preferential flow contributing to aquifer recharge increased. With the increase of rainfall amount, the duration of aquifer recharge lengthened. 相似文献
268.
May Than Thar Cho Anusron Chueasamat Toshikazu Hori Hirotaka Saito Yuji Kohgo 《Soils and Foundations》2021,61(2):480-495
Slope failures due to heavy rainfall events are phenomena that can cause serious damage to social infrastructures and the loss of lives. Based on previous studies, natural slope failures are generally shallow and originate at the slope toe where infiltrated rainwater has accumulated and saturated it. Hence, it is extremely important to prevent these initial failures from inducing entire slope failures. In the present study, firstly, 1 g model tests, called G series tests, were conducted. In the tests, a gabion filled with filter materials was placed at the slope toe of each model for reinforcement and to drain the accumulated rainwater from the slope toe. Filter gabions have been found to shrink the failure regions and to significantly extend the time until slope failures occur. The failure mechanism in the G series tests was almost similar to that in cases without filter gabions if focus was placed on the slope above the filter gabions. However, the drainage effect was small. Secondly, P series tests, in which a filter gabion with a pipe was introduced for each model, were conducted. The results of these tests indicated that the displacements significantly decreased as the diameter of the pipe and the depth of the pipe’s insertion to the surface layer increased. Water did not discharge through the pipe until the pore water pressure around the pipe reached positive values. The failures always started when a phreatic surface appeared on the slope surface. Thus, it is very important to prevent a phreatic surface from forming on the slope surface. The adequate arrangement of a filter gabion with a drainage pipe may increase the potential for slope stability. 相似文献
269.
270.