Characteristics of rainfall and runoff in different extreme precipitation events in the Beijing mountain area

This study was based on a rainstorm that happened in Beijing on 20 July 2016. We analyzed the characteristics of rainfall and runoff during this rainstorm, compared it to rainstorm 721, and investigated why no surface runoff was observed during this rainstorm. A runoff plot experiment showed that almost all runoff consisted of deep interflow (40–60 cm). For runoff plots with identical vegetation, the slope was smaller, and the lag time of the deep interflow relative to the process of rainfall was shorter. The runoff yield of the deep interflow was inversely proportional to the slope. Compared to plots with pure tree forest and shrub forest, the interflow process curve of plots with coniferous and broad-leaved mixed forest was relatively gentle during the rainfall process. Thick litter layers, low antecedent moisture content of the soil, high gravel content of the soil, and the short duration of high intensity rainfall are the causes for the observed lack of surface runoff. To simultaneously prevent flooding and waterlogging, we propose to utilize vegetation to improve water storage at the reservoirs and to replenish the groundwater during cumulative rainstorms with a stable rain tendency.

Interrill erosion, runoff and sediment size distribution as affected by slope steepness and antecedent moisture content

Soil erosion is a two-phase process consisting of the detachment of individual particles and their transport by erosive agents such as flowing water. The rate at which erosion occurs depends upon the individual as well as interactive effects of different parameters responsible for soil erosion. The study discusses results of a laboratory analysis and evaluates the effect of slope steepness and antecedent moisture content on sediment yield (wash) and runoff rate. Interrill sediment yield, splash detachment, runoff, and sediment size distribution were measured in laboratory erosion pans under simulated total duration of 90 min. Rainfall intensity at 120 mm/hr, 70 mm/hr, and 55 mm/hr were applied sequentially at 9, 25, and 45% slope steepness for three soils (Alemaya Black soil, Regosols, and Cambisols) varied from clay to sandy clay loam in texture with wet and dry antecedent water contents. As slope steepness increased from 9 to 25% splash increased for five treatments and decreased for the remaining treatment; washed sediment increased for all treatments. As slope increased from 25 to 45% splash decreased for five treatments but increased for one treatment, and washed sediment increased for three treatments but decreased for the other three treatments. Pre-wetting decreased splash detachment for all soil treatments and rate of reduction was high for the highly aggregated soil, Alemaya Black soil and low for the less aggregated soil Regosols. Splash sediment and sediment yield was not correlated. Change in splash with increase in slope steepness was also not correlated with change in sediment yield. Change in runoff rate with increase in slope steepness was correlated (r=0.66) with change in sediment yield. For Alemaya Black soil and Regosols, splashed sediment size distribution was correlated with washed sediment size distribution. Interrill erosion models that include runoff and rainfall intensity parameters were a better fit for these data than the rainfall intensity based model. The exponent term, b, values in (E=a Ib) model did not approach 2.00 for all treatments. For the same slope steepness factor, both rainfall and rainfall-runoff based models provided different erodibility coefficients at different levels of slope and moisture contents.

Kajian Model Estimasi Volume Limpasan Permukaan, Debit Puncak Aliran, dan Erosi Tanah dengan Model Soil Conservation Service (SCS), Rasional Dan Modified Universal Soil Loss Equation (MUSLE) (Studi Kasus di DAS Keduang, Wonogiri)

Hydrologic modelling has been developing and it is usefull for basic data in managing water resources. The aim of the reseach is to estimate volume runoff, maximum discharge, and soil erosion with SCS, Rational, and MUSLE models on Keduang Watershed. Explain the data analysis, and flow to get the data. SCS parameters model use are: runoff, rainfall, deferent between rainfall runoff. The deferent rainfall between runoff relationship kurva Runoff Coefisient (Curve Nunmber/CN). This Coefisient connected with Soil Hydrology Group (antecedent moisture content/AMC), landuse, and cultivation method. Rational parameters model use are: runoff coefisient, soil type, slope, land cover, rainfall intensity, and watershed areas. MUSLE parameters model use are: rainfall erosifity (RM), soil erodibility (K), slope length (L), slope (S), land cover (C), and soil conservation practice (P). The result shows that the conservation service models be applied Keduang Watershed, Wonogiri is over estimed abaut 29.54 %, Rational model is over estimed abaut 49.96 %, and MUSLE model is over estimed abaut 48.47 %.