延河流域径流泥沙变化及其驱动因素研究

近几十年来，受气候变化和人类活动的双重影响，流域的水文特征变化日益加剧，而河道径流、泥沙量是其中变化较为明显的水文因子。退耕还林工程实施以来，黄河的径流泥沙呈现减少趋势，河道水沙特征发生明显改变，位于黄河流域的延河流域水沙变化也呈现同样特征。本文以黄土高原延河流域为研究对象，通过搜集流域内1960年~2010年降水、径流、泥沙实测年数据资料及1980年~2010年植物生长季(5月~10月)NDVI的月均值等数据资料，采用线性趋势法、距平累积曲线法、双累积曲线法等统计分析方法，研究流域内主要水文数据的趋势性、阶段性、旱涝丰枯特征及耦合关系，并分析降水量、植被覆盖度与径流量、输沙量之间的偏相关性。并运用无截距双累积曲线定量分割流域内降水变化和水土保持活动对水沙变化的影响程度。在此基础上选择试验因子，通过观测野外径流小区，利用汛期天然降水，探究不同坡面植被措施的减水减沙规律。研究得到如下主要结论:延河流域的径流量和泥沙量近51年来均呈现震荡性下降趋势，震荡性变化具有相似性，线性倾向率分别为-0.19×108 m3/10a和-0.09×108 t/10a。水沙发生突变的年份为1971年和1996年，据此可分为三个主要阶段，径流年型多为枯水年且历时长度逐渐增大。河道输沙量与径流量呈现水大沙则多，水小则沙少的显著正相关关系。2013年7月~9月延河各主要水文站平均径流量为历年最大值，7月份径流量超过多年平均值的4.1倍以上。同期延河流域坡面植被小区产流产沙特点为:产流次数少，产流率略小，产流量明显减少，产沙量接近于0。1960年~2010年期间年降水量呈微弱下降趋势，线性倾向率为-15.5mm/10a，降水量年际变化差异相对较小，变差系数为0.202。流域内降水量阶段性变化特征不明显，整体保持在随机波动状态下发生，可简单分为1960~1971年、1972~1996年和1997~2010年三个主要阶段。延河流域50年的正常降水年发生概率达78.4%。2013年7月~9月降水量占全年降水量的91%，7月极端降水呈现降水量大、降水历时长、次降水间隔时间短的明显特征。20世纪60年代以来，延河流域开展的一系列水土保持活动成效显著，不同阶段开展的水土保持措施各有侧重。截至2006年底，延河流域内各项水土保持措施实施面积为2 698.42 km2，治理程度53%，其中林草植被实施面积为2 370.05 km2。1980年~2010年期间，流域植被覆盖情况逐年加速改善。1999年之后增加程度更加明显，植被覆盖率的平均线性增长率为0.258/10a。截止到2008年底，延安市累计完成国家计划内退耕还林面积58.8l×103 km2。降水量与径流量、输沙量的双累积线性增加关系的拟合优势度R2大于0.97，拟合程度较高。1960~2010年期间，流域下垫面的变化对降水变化的主导地位产生了一定的削弱作用，流域产流产沙对降水量变化的响应程度逐渐变弱。在降水量变化差异不大的情况下，流域水沙关系发生了根本变化且总体表现为流域产流产沙量减少。1999年以后，流域植被覆盖度线性增加趋势显著，相异于径流深和输沙模数的明显下降趋势。降水量与径流深及输沙模数的偏相关系数分别为0.705和0.414;植被覆盖度与径流深及输沙模数的偏相关系数分别为-0.705和-0.563。以1960年~1971年为基准期构建降水量与径流深和输沙模数的无截距线性双累积方程，得到的线性拟合方程分别为xyr?0723.0和xys?0018.0(ry为年径流深，sy为年输沙模数，x为年降水量)。1997-2010年期间以植被恢复为主导的水土保持措施减流减沙贡献率分别为12.87%和52.29%。不同土地利用下坡面产流之间存在差异，坡面草被覆盖下坡面产水产沙量明显小于裸地小区产流产沙量，7月、8月是流域的坡面产沙敏感时段。坡面植被小区减沙率基本接近于100%，7月、8月植被减流率在85%以上。

In recent decades, hydrological characteristics of river basins have undergone increasingly drastic changes under the dual influences of climate change and human activities, among which stream runoff and sediment load are the most prominent hydrological factors. Since the implementation of the Grain for Green Project, the runoff and sediment load of the Yellow River have shown a decreasing trend, and the water and sediment characteristics of the river channel have changed significantly. The Yanhe River Basin, located in the Yellow River Basin, exhibits the same characteristics of water and sediment changes.
This paper takes the Yanhe River Basin on the Loess Plateau as the research object. By collecting annual measured data of precipitation, runoff and sediment load in the basin from 1960 to 2010, as well as monthly mean NDVI data during the plant growing season (May to October) from 1980 to 2010, and adopting statistical analysis methods including linear trend method, anomaly accumulation curve method and double mass curve method, we investigate the trend, stage characteristics, drought-flood and runoff-sediment variation characteristics, and coupling relationship of main hydrological data in the basin. In addition, we analyze the partial correlations between precipitation, vegetation coverage, runoff and sediment load. Moreover, the intercept-free double mass curve is used to quantitatively separate the impact degrees of precipitation change and soil and water conservation activities on water and sediment changes in the basin. On this basis, experimental factors are selected, and the runoff and sediment reduction rules of different slope vegetation measures are explored by observing field runoff plots and using natural precipitation during flood seasons.
The main research conclusions are as follows: Both the runoff and sediment load of the Yanhe River Basin have shown a fluctuating downward trend over the past 51 years, with similar fluctuating changes, and the linear trend rates are -0.19×10^8 m³/10a and -0.09×10^8 t/10a, respectively. The abrupt change years of water and sediment are 1971 and 1996, based on which the basin can be divided into three main stages. The annual runoff types are mostly dry years, and the duration of dry years gradually increases. There is a significant positive correlation between channel sediment load and runoff, that is, more runoff corresponds to more sediment and less runoff corresponds to less sediment. The average runoff of the main hydrological stations in the Yanhe River from July to September 2013 was the highest in history, and the runoff in July exceeded 4.1 times the multi-year average. The characteristics of runoff and sediment yield in the slope vegetation plots of the Yanhe River Basin during the same period are: fewer runoff events, slightly lower runoff rate, significantly reduced runoff volume, and sediment yield close to 0. From 1960 to 2010, the annual precipitation showed a slight downward trend, with a linear trend rate of -15.5 mm/10a. The inter-annual variation difference of precipitation is relatively small, with a coefficient of variation of 0.202. The stage change characteristics of precipitation in the basin are not obvious, and it generally occurs under random fluctuations, which can be simply divided into three main stages: 1960~1971, 1972~1996 and 1997~2010. The occurrence probability of normal precipitation years in the Yanhe River Basin over 50 years reaches 78.4%. Precipitation from July to September 2013 accounted for 91% of the annual precipitation. The extreme precipitation in July was characterized by large precipitation amount, long duration and short interval between consecutive precipitation events. Since the 1960s, a series of soil and water conservation activities carried out in the Yanhe River Basin have achieved remarkable results, and the soil and water conservation measures implemented in different stages have their own focuses. By the end of 2006, the implemented area of various soil and water conservation measures in the Yanhe River Basin was 2698.42 km², with a management degree of 53%, among which the implemented area of forest and grass vegetation was 2370.05 km². From 1980 to 2010, the vegetation coverage of the basin has improved year by year at an accelerating rate. The improvement became more obvious after 1999, with an average linear growth rate of 0.258/10a for vegetation coverage. By the end of 2008, Yan'an City had completed a total of 58.81×10^3 km² of state-planned converted farmland to forest area. The goodness of fit R² of the linear double mass increasing relationship between precipitation, runoff and sediment load is greater than 0.97, indicating a high fitting degree. From 1960 to 2010, the changes in the underlying surface of the basin have weakened the dominant position of precipitation changes to a certain extent, and the response of runoff and sediment yield to precipitation changes has gradually weakened. When the difference in precipitation changes is small, the water and sediment relationship of the basin has undergone fundamental changes, generally showing a decrease in runoff and sediment yield. After 1999, the linear increasing trend of vegetation coverage in the basin was significant, which was different from the obvious downward trend of runoff depth and sediment transport modulus. The partial correlation coefficients between precipitation and runoff depth, as well as between precipitation and sediment transport modulus, are 0.705 and 0.414, respectively; the partial correlation coefficients between vegetation coverage and runoff depth, as well as between vegetation coverage and sediment transport modulus, are -0.705 and -0.563, respectively. Taking 1960~1971 as the baseline period, the intercept-free linear double mass equations between precipitation and runoff depth, as well as between precipitation and sediment transport modulus, were established, and the linear fitting equations are ry = 0.723x and sy = 0.0018x (where ry is annual runoff depth, sy is annual sediment transport modulus, and x is annual precipitation). From 1997 to 2010, the contribution rates of vegetation restoration-dominated soil and water conservation measures to runoff and sediment reduction were 12.87% and 52.29%, respectively. There are differences in slope runoff under different land uses. The runoff and sediment yield of slope plots covered with grass are significantly less than those of bare land plots. July and August are the sensitive periods for slope sediment yield in the basin. The sediment reduction rate of slope vegetation plots is basically close to 100%, and the vegetation runoff reduction rate in July and August exceeds 85%.

搜集汇总

背景与挑战

背景概述

该数据集研究了1960年至2010年期间延河流域的径流和泥沙变化趋势，分析了气候变化和人类活动（如退耕还林）对水文特征的影响。研究采用了多种统计方法，发现径流量和泥沙量呈震荡性下降趋势，并量化了水土保持措施对减流减沙的贡献率。