Using the modified agricultural non-point source pollution model in German watersheds

The modified agricultural non-point source pollution model (AGNPSm) was used in this study to predict runoff volume, peak flow rate, and sediment yield in three different watersheds in Germany. It is a distributed parameter soil erosion model which uses simple approaches to hydrological and sediment calculations. Simulations were carried out in the Glonn G1 (1.2 km²), and Glonn G2 (1.6 km²), and the Salzboede (81.7 km²) watersheds in Germany. Runoff volume was predicted reliably in all three watersheds. Sediment yield predictions were excellent in the Glonn G1 and acceptable in the Glonn G2 watersheds. There were some uncertainties in the sediment yield calculations for the Salzboede watershed. This study shows that a less complex soil erosion model such as AGNPSm is able to produce reliable assessments of non-point source pollution for planning purposes.     

黄河中游典型流域近60年水沙变化趋势及影响因素

为分析黄河水沙成因并预测未来水沙情势,选取黄河中游多沙粗沙区昕水河和朱家川2条流域为研究对象,依据水文站及雨量站1956—2018年降雨和径流泥沙实测数据,采用Mann-Kendall趋势及突变检验、累积距平法和Morlet连续小波分析等方法探讨流域水沙变化趋势,并利用双累积曲线法对水沙变化进行归因分析,量化气候变化及人类活动对水沙变化的相对贡献。结果表明:1956—2018年,昕水河和朱家川小流域年均径流量分别为11.9×10⁷,1.7×10⁷ m³,年均输沙量分别为12.3×10⁶,9.8×10⁶ t,径流和输沙量均呈显著减少趋势;2条流域的径流量突变年分别为1980年和1984年,输沙量突变年分别为1980年和1972年;选取的2条流域水沙变化存在明显周期性,径流变化的第1主周期分别为45年和16年,输沙量变化的第1主周期分别为9年和15年;降雨对昕水河和朱家川小流域径流量减少的贡献率分别为19%,8%,对输沙量减少的贡献率分别为25%,35%,远不及人类活动的贡献率,人类活动是径流和输沙量锐减的主导因素。研究结果可为黄河水沙治理提供科学性建议。     

黄土丘陵沟壑区不同空间尺度流域泥沙输移比研究

泥沙输移比是定量表征流域内侵蚀产沙-河道输沙特征的重要指标。探讨了不同尺度流域泥沙输移比计算的可能性与方法,以黄土丘陵沟壑区的径流小区、小流域、水文站实测资料为基础,利用径流小区观测资料和单元小流域侵蚀模数2种方法,对4种空间尺度流域的泥沙输移比进行了估算。结果表明:(1)对于面积在10~100km²的小流域,利用2种方法计算的泥沙输移比结果非常接近,说明在没有小区观测资料时,用单元小流域计算流域泥沙输移比是可行的。(2)对于土壤侵蚀类型单一的水文站控制流域,在没有面积>1km²单元小流域资料的情况下,可以用面积1~10km²小流域或面积10~100km²小流域作为单元小流域来计算泥沙输移比而对于侵蚀类型不同的支流其误差范围有些偏大。(3)流域治理措施的实施对于泥沙输移比的减少具有明显的效果,但治理措施减沙效应的发挥具有一定的滞后性。     

岔巴沟流域泥沙输移比时空分异特征及影响因素

本文以团山沟单元小流域作为流域系统产沙的源地，将其它中小流域输沙模数与单元小流域侵蚀模数之比定义为泥沙输移比，系统的研究了岔巴沟流域次暴雨泥沙输移比的时空变化特征及降水水文影响因子和地貌形态因子的综合影响。研究发现，从长远来看，流域系统的侵蚀与产沙可达到平衡，但就次降雨或年度而言，流域系统经常处于泥沙滞留和滞留的泥沙重新侵蚀搬运的状态。降雨量、径流系数、降雨时间、水流平均含沙量能很好的表达岔巴沟各流域次暴雨泥沙输移比，在考虑地貌形态因子的影响后，得到了岔巴沟流域次暴雨泥沙输移比的降水水文因子与地貌形态因子关系的综合表达式。     

Prediction of soil and water conservation structure impacts on runoff and erosion processes using SWAT model in the northern Ethiopian highlands

Purpose

Land degradation due to soil erosion is a serious threat to the highlands of Ethiopia. Various soil and water conservation (SWC) strategies have been in use to tackle soil erosion. However, the effectiveness of SWC measures on runoff dynamics and sediment load in terms of their medium- and short-term effects has not been sufficiently studied.

Materials and methods

A study was conducted in 2011 to 2015 in the Gumara-Maksegnit watershed to study the impacts of SWC structures on runoff and soil erosion processes using the soil and water analysis tool (SWAT) model. The study was conducted in two adjacent watersheds where in one of the watersheds, SWC structures were constructed (treated watershed (TW)) in 2011, while the other watershed was a reference watershed without SWC structures (untreated watershed (UW)). For both watersheds, separate SWAT and SWAT-CUP (SWAT calibration and uncertainty procedure) projects were set up for daily runoff and sediment yield. The SWAT-CUP program was applied to optimize the parameters of the SWAT using daily observed runoff and sediment yield data.

Results and discussion

The runoff simulations indicated that SWAT can reproduce the hydrological regime for both watersheds. The daily runoff calibration (2011–2013) results for the TW and UW showed good correlation between the predicted and the observed data (R ²?=?0.78 for the TW and R ²?=?0.77 for the UW). The validation (2014–2015) results also showed good correlation with R ² values of 0.72 and 0.70 for the TW and UW, respectively. However, sediment yield calibration and validation results showed modest correlation between the predicted and observed sediment yields with R ² values of 0.65 and 0.69 for the TW and UW for the calibration and R ² values of 0.55 and 0.65 for the TW and UW for the validation, respectively.

Conclusions

The model results indicated that SWC structures considerably reduced soil loss by as much as 25–38% in the TW. The study demonstrated that SWAT performed well for both watersheds and can be a potential instrument for upscaling and assessing the impact of SWC structures on sediment loads in the highlands of Ethiopia.

     

Hydrosedimentology of nested subtropical watersheds with native and eucalyptus forests

Purpose

Information on the effects of eucalyptus forests on hydrosedimentological processes is scarce, particularly at the catchment scale. Monitoring and mathematical modeling are efficient scientific tools used to address the lack of information for natural resource management and the representation and prediction of those processes. This study evaluates the effects of eucalyptus cultivation on hydrosedimentological processes in watersheds and to use the Limburg soil erosion model (LISEM) to represent and predict hydrological processes.

Material and methods

The study was conducted in two forested watersheds: the main watershed (94.46 ha) and a nested sub-watershed (38.86 ha), both cultivated with eucalyptus and residual riparian native forest, located in southern Brazil. Hydrosedimentalogical monitoring was conducted from 16th February 2011 to 31st December 2012, and LISEM model calibrations were performed on the bases of six storms events.

Results and discussion

The sediment yield for 2011 was 41.6 Mg km^?2 and 38.5 Mg km^?2 for the watershed and sub-watershed, respectively. An extreme event in 2012 provided greater sediment yield for the sub-watershed (99.8 Mg km^?2) than that for the watershed (51.7 Mg km^?2). Rainfall events with a greater maximum intensity generated rapid discharge and suspended sediment concentration responses in the sub-watershed due to the smaller drainage area and steeper landscape. In the main watershed, the accumulation of flood waves occurred for most events, with less steep hydrographs, and a later occurrence of the discharge peak after that of the sub-watershed. The LISEM adequately reproduced the peak discharge and runoff for the calibrated events; however, the peak time and the shape of the hydrograph were not adequately represented.

Conclusions

The hydrosedimentological patterns of the watershed and sub-watershed, both cultivated with eucalyptus, was characterized by sedimentographs preceding hydrographs during rainfall–runoff events where scale effects occur, with maximum discharge and specific sediment yield greater in the watershed than that in the sub-watershed. Empirical models based on hydrologic variables may be used for estimating the suspended sediment concentration and sediment yield. Therefore, LISEM may be used for the prediction of hydrological variables in these forested watersheds.     

Estimating Sediment Delivery Ratios for Grassed Waterways using WEPP

Grassed waterways (GWWs) transport sediment and nutrients from upland source areas to receiving waters. Watershed planners have a critical need to understand GWW sediment delivery to optimally target source area management practices. Better physically based tools are needed to estimate sediment delivery by GWWs. This study developed several distributed sediment delivery ratio (SDR) regressions for GWWs using the process‐based Water Erosion Prediction Project (WEPP) model to provide simple equations to estimate sediment delivery for planning applications. Water Erosion Prediction Project was calibrated and validated for runoff and sediment yield for large 30.2‐ha and smaller 5·7‐ha nested watersheds with terraces and a common GWW outlet. A crop rotation of corn, oat and alfalfa and fall tillage using chisel plow were used in the nested watersheds. A hypothetical management case without terraces using corn, oat and alfalfa rotation with chisel plow as fall tillage was also evaluated for the 5·7‐ha watershed and the GWW. The length, slope, Manning's roughness coefficient and infiltration rate for the GWW were varied and SDRs calculated for 30 representative (in terms of daily rainfall) days over a 20‐year period of simulated climate. Regressions were developed for the existing (terraced) and hypothetical (non‐terraced) management scenarios for early (April–July), late (August–October) and full (April–October) growing seasons. Equations developed for the non‐terrace watershed had higher R ² values compared to the terraced watershed suggesting that channel and rainfall parameters were better able to explain the variation in SDR for the non‐terraced watershed. Manning's roughness coefficient was the most significant parameter for predicting SDR for both the terraced and non‐terraced watersheds. The equations developed here can be used to estimate SDRs for watersheds that are drained via GWWs having similar physical characteristics: slope (1–5%), Mannings's roughness coefficient (0·1–0·3), length (0·15–1 km) and infiltration rate (0·025–25 mm h⁻¹). The SDRs can be used to estimate sediment yield, which is an essential element for making land management decisions but is rarely measured. Copyright © 2017 John Wiley & Sons, Ltd.     

黄土高原粗泥沙集中来源区水沙变化特征及趋势性分析

黄土高原粗泥沙集中来源区为治理黄河泥沙的重点核心地区.根据1960-1999年黄土高原粗泥沙集中来源区皇甫川、孤山川I、窟野河,秃尾河和佳芦河径流及输沙资料,以流域为单元,分析了区内各流域径流量、输沙量的年内、年际变化特征及变化趋势.结果表明,区内径流量及输沙量的年际、年内变化较大.在季节上,除秃尾河径流量集中期为6月份外,其余4条流域径流量的集中期均为8月份;5条流域输沙量的集中期均为8月份.各流域径流量、输沙量的突变时间均在20世纪70年代,说明各流域水沙量呈现减少的趋势,尤以20世纪90年代减少最明显.人类活动和气候变化是影响该区内各流域水沙变化的主要因素.     

松花江流域侵蚀产沙演变特征分析

利用松花江流域116个站点的降水资料和14个典型流域水文站的径流泥沙资料,在分析降水、径流和输沙时间变化特征的基础上,研究了该区侵蚀产沙演变特征及其主要影响因素.研究结果表明,1961-1990年松花江流域降水和径流无显著增长趋势,但输沙量增长显著,每10 a平均增长幅度为34.7%,丘陵漫岗区输沙量增长幅度较山区更为显著.流域输沙量自1979年开始显著增加,降水量变化不是输沙量快速增长的主要原因,人类活动导致的下垫面变化可能是输沙量增加的重要原因.     

基于SWAT模型的罗玉沟流域森林植被变化的水文生态响应研究

以甘肃天水罗玉沟流域为研究区,应用分布式水文模型（SWAT）对该流域的径流、泥沙和水质状况进行模拟研究,并重点探讨了降雨和森林植被变化对水文生态响应的影响。结果表明:降雨因子对径流的影响略大于对泥沙的影响;森林植被具有明显的减水减沙生态水文功能,尤其对泥沙的影响更大于对径流的影响。     

Temporal variability of rainfall in a semiarid environment in Brazil and its effect on sediment transport processes

Purpose

The temporal variabilities of both soil erosion by water and sediment redistribution in watersheds are directly related to rainfall characteristics. The purpose of this work was to assess the temporal pattern of rainfall in a semiarid watershed in Brazil and explain how this feature controls soil erosion and sediment yield.

Materials and methods

Daily and 5-min rainfall records were used to assess the temporal pattern down to the sub-hourly scale. To study the effect of the rainfall on sediment processes, erosivity and sediment yield at the Aiuaba (12 km²) and Benguê (933 km²) watersheds, Brazil were determined. Erosivity was calculated based on the rainfall kinetic energy method, while sediment yield was estimated from sediment rating curves and daily water discharge measurements.

Results and discussion

A large portion of annual rainfall is restricted to a few rain events and strong concentration in the sub-daily scale occurs, producing high erosivity. The temporal concentration of erosivity is greater than that of rainfall; the 10th percentile of the highest magnitude events encompasses 51% of the precipitation, but 80% of the erosivity. The temporal concentration of sediment yield is more pronounced; 88 and 98% of the sediment yield for the Aiuaba and Benguê watersheds, respectively, are within the 10th percentile of events.

Conclusions

The strong temporal concentration of precipitation causes events with high intensity and erosivity, thus allowing for soil detachment. Nonetheless, the low runoff rates limit downstream sediment transport. Such behavior produces a much higher temporal concentration of sediment yield, which reaches its maximal after a sequence of rainy days, when hydrological connectivity is enhanced and the sediments are propagated throughout the entire transport-limited system.     

四川省紫色土地区小流域次降雨泥沙输移比探讨

选取四川省南部县鹤鸣观小流域与李子口小流域为研究区,在分布式侵蚀产沙模型侵蚀量计算值的基础上,探讨了小流域次降雨泥沙输移比.结果表明,在这两个流域,影响次降雨泥沙输移比的主要因素不同.在鹤鸣观小流域降雨量与径流深是影响泥沙输移比的主要因素,而在李子口流域,其主要因素为径流深与降雨强度.主要原因是鹤鸣观小流域的面积远小于李子口流域的面积,并且次降雨泥沙输移比随着流域面积增加而输移比逐渐减小.通过分析鹤鸣观小流域与李子口小流域次降雨泥沙输移比与降雨量、前期含水量、径流系数的关系得到了两个流域次降雨泥沙输移比公式.     

黄土丘陵沟壑区吕二沟流域水沙关系变化分析

流域水沙关系的研究可为流域水土流失模型构建和水土保持效益评价提供科学依据。根据黄土丘陵沟壑区第三副区的吕二沟流域在1982--2010年间的74场次洪水事件水文泥沙数据,对降雨、径流和输沙的关系进行分析,并用Mann—Kendall法检验流域次洪水事件径流系数和平均含沙量的变化趋势和显著性。结果显示,降雨量和降雨历时是流域径流和输沙的主要影响因素,前期降雨量中前7天降雨量与径流系数的相关性最显著。吕二沟流域具有较好的水沙关系。通过Mann．Kendall法检验得到1985年8月24日发生的洪水事件是流域径流系数时间序列的突变点,突变点之后径流系数呈显著减小趋势,植被覆盖面积的增加是流域降雨一径流关系发生变化的主要原因。流域次洪水事件平均含沙量时间序列没有发生显著变化,表明以植物措施为主的水土流失综合治理没有显著影响吕二沟流域的水沙关系。     

黄龙山区不同类型小流域的产流过程及其特征

 在黄龙山区选择自然条件基本相似的森林小流域、森林采伐小流域和荒坡草灌小流域,利用量水堰,于1999—2003年对流域的产流及其过程进行了系统的研究。结果表明:不同类型小流域径流的年际和年内变化不同。森林小流域全年产流,产流量主要与降水量有关;荒坡草灌小流域则仅在暴雨季节产流,产流量主要与雨强有关。除发生特大暴雨年份外,森林小流域的产流量均超过荒坡草灌小流域,5年内平均前者比后者多3倍。不同类型小流域对降水的调节作用不同,5年平均森林小流域比荒坡草灌小流域减少洪水径流94.9%,达5.2mm,增加枯水期径流0.5mm,占年径流量的8.7%,从而使流域径流保持相对均匀和稳定。采伐森林可以改变小流域的径流分布,常年径流被暴雨径流所代替,但其量比荒坡草灌小流域少。不同类型小流域产流过程不同,森林小流域产流过程平缓,洪水起伏程度小;而荒坡草灌小流域产流曲线陡峭,洪峰形成迅速,回落也较快。     

神木六道沟气候及地面组成物质特征对侵蚀产沙影响分析

在野外调查与试验研究的基础上,分析了六道沟及其相邻流域降雨、径流、气温、风力等气候因素及地面组成物质特征对侵蚀产沙的影响。认为暴雨强度大,疾风多、植被少,地面组成物质复杂松散,以及不良的土壤理化特性,是该区侵蚀产沙特别强烈的根本原因,该区的侵蚀具有复杂多样的特殊性,在时间与空间上差异较大,分布不均;地面物质粗、产沙量大、是粗沙的主要产区;掌握侵蚀特点,控制风沙直接入沟,入河及坡耕地的改造,防治沟头,沟壑崩塌,扩大草灌,发展多样性农业为治理重点。     

泾河典型流域水沙变化及其景观格局分析

以黄河中游泾河流域的3个子流域为研究对象,借助GIS和RS技术与基本的水沙数据,分析各子流域水沙变化特点与土地覆被空间格局特征。结果表明:流域北部的环江上游、合水川与汭河的径流量和输沙量以及土地覆被空间格局分布差异显著;30多年来环江上游的径流量增加了60%而输沙量却增加了1倍多,汭河的径流量减少了约40%而输沙量却减少到1/5,合水川的径流量基本保持不变而输沙量略有增加;环江上游只有6种土地覆被类型以低密度草地和半荒漠草地为主,汭河有9种土地覆被类型以林地、农田和高密度草地为主,合水川有7种土地覆被类型以林地和郁闭灌丛为主。     

基于径流侵蚀功率的长江典型流域能沙关系模型及改进

基于径流侵蚀功率概念建立流域能沙关系模型,可为长江流域泥沙变化精准模拟与水土保持规划提供技术支撑。该研究以长江典型流域及其典型小流域为研究对象,通过收集1965—2018年金沙江流域、嘉陵江流域和湘江流域3个典型流域逐日水沙数据以及万安和李子口2个典型小流域2014—2020年场次降水径流泥沙数据,采用径流侵蚀功率、径流量和降雨侵蚀力对比分析不同时空尺度水沙(径流量和输沙量)、雨沙(降雨侵蚀力和输沙量)和能沙(径流侵蚀功率和输沙量)关系的优劣性,解析能沙关系优越性,并识别能沙关系非一致性变化,从而改进能沙关系模型提高流域输沙量模拟精度。结果表明：1)长江流域3个典型流域及2个典型小流域,在绝大部分情况下能沙关系的表现总是优于水沙关系和雨沙关系,在场次、月和年尺度修正的决定系数最大值分别可达到0.94、0.87和0.54。2)对于不同时间尺度,其流量序列中任意2个流量乘积与输沙量的相关性较高时,第一个流量Q₁分位点总是接近1且第二个流量Q₂分位点在0.5附近或者高于0.5。基于径流侵蚀功率可以较为准确地计算不同时空尺度流域输沙量,具有明显适用性...     

Evaluation of Sediment Deposition in a Mediterranean Reservoir: Comparison of Long Term Bathymetric Measurements and SWAT Estimations

This study aims to demonstrate that the SWAT model can be used to predict discharge and sediment yield values in reservoir contributing catchments helping also to define the main factors that determine sedimentation rates in semi‐arid Mediterranean environments. This aim was achieved by comparing SWAT simulation results with water flows (over 29 years) and sediment deposition (over 47 years) volumes collected (by a campaign of bathymetric surveys) in a Sicilian reservoir. The mean monthly runoff coefficient calculated for the period 1980–2008 was 0·17. The mean sedimentation volume in the reservoir during the period 1963–2009 was 51,000 m³ year⁻¹. Field surveys and collection of spatially distributed databases of soil, topography and climate were carried out in order to characterize the contributing catchment. The SWAT model was applied to simulate sediment volumes cumulated over group of years as well as water flow volumes reaching annual and monthly the reservoir. The performance of the hydrological and erosion components of the model was evaluated by a combination of both summary and difference statistical measures after a sensitivity analysis and a calibration/validation process. The model was able to simulate observed runoff volumes at both annual and monthly scale. The mean sedimentation volume simulated by SWAT during the whole period was 8·1% lower than the value obtained by the bathymetric measurements (equal to 72·10³ Mg) with very good values of the efficiency coefficient (equal to 0·91). Copyright © 2016 John Wiley & Sons, Ltd.     

黄土高原丘陵沟壑区临界地貌侵蚀产沙特征

深入研究流域临界地貌形态对侵蚀产沙的作用机制至关重要,也是建立流域侵蚀产沙预测模型的关键所在。该研究以黄土高原丘陵沟壑区岔巴沟为研究对象,开展了流域次降雨侵蚀产沙的BP人工神经网络(back propagation artificial neutral network,BPANN)模型与多重线性回归(multiple linear regression,MLR)模型比较研究,定量分析了流域侵蚀产沙的敏感因子及影响程度,并使用分形信息维数临界值和相对应的变量建立临界地貌侵蚀产沙预测模型,阐明临界地貌侵蚀产沙特征。结果表明,在侵蚀产沙模数预测方面,BPANN模型较MLR模型具有更好预测性能,能够有效表征综合条件下侵蚀产沙的动态变化过程。径流深和径流侵蚀功率对侵蚀产沙以及水文响应的影响程度受地貌形态因素制约。当分形信息维数大于地貌临界值时,采用径流侵蚀功率的预测精度高于径流深;相反,分形信息维数小于地貌临界值时,采用径流深的预测精度高于径流侵蚀功率。以分形信息维数为界,分别引入径流深或径流侵蚀功率所建立的临界地貌侵蚀产沙预测模型,具有较高的预测精度,具有一定的可行性、可靠性和普适性。     

Sediment Yield Deduction from Check–dams Deposition in the Weathered Sandstone Watershed on the North Loess Plateau,China

As the basic unit of erosion and sediment yield, it was critical to determine the amount of soil erosion and sediment yield in the small watersheds for sustaining a reasonable water resource and sediment regulation system. In this study, we determined the sediment yield from the dams‐controlled watershed on the North Loess Plateau. Three check dams in the watershed were investigated by drilling ten‐hole sedimentation cores. The corresponding flood couplets were dated according to thickness of deposition layers, distribution of sediment particle size and historical erosive rainfall events. On the basis of the check dams capacity curve, the soil bulk density and the thickness of couplets, the deposit mass of check dams, and then the sediment yield of watershed at different temporal and spatial scale were deducted. In total of the 33, 60 and 55 couplets were corresponded to individual flood events in the dam MH1# from 1976 to 1984, the dam MH2# from 1985 to 2007, and the dam MH4# from 1981 to 2009, respectively. The specific sediment yield for flood events was 1,188.5–11,527.9 Mg km⁻², 1,278.6–17,136.7 Mg km⁻², and 3,395.9–33,698.5 Mg km⁻², and the annual average sediment yield was 10,728.6 Mg (km² · a)⁻¹, 12,662.9 Mg (km² · a)⁻¹, and 16,753.3 Mg (km² · a)⁻¹ in dam MH1#, MH2# and MH4# controlled watershed, respectively. The sediment yields were inversely proportional to the dams – controlled areas. For the whole watershed, the annual average sediment yield was 14,011.1 Mg (km² · a)⁻¹ from 1976 to 2009. There were large amounts of sediments (42.3–50.5%) were intercepted gradually along the way from small watersheds to the river channel. And the minimum rainfall for sediment deposited in the dams was greater than 20 mm in this watershed. The results of this study suggested that the sediments retained behind check dams were helpful to quantifying the amount of erosion sediment yield and understanding the soil erosion evolution in the small and ungauged watersheds. Copyright © 2016 John Wiley & Sons, Ltd.