岩溶槽谷区水土流失特征及机理研究

Karst terrain is extensively districted South-west China where heavily populated communities suffer from serious soil erosion and increasing rocky desertification.This situation became so acute that Government made the call "to further enhance the management of soil erosion in Southwest China"as reflected in the Central Committee No. 1 Document in 2011, requesting "strengthening the comprehensive management of desertification" in Twelve oFive-Year" Plan. To implement the Government's policy effectivly, it is essential to understand the mechanisms of soil erosion and desertification process. Comparied with non-karst area, soil leakage in karst region is a profound phenomenon. As neither a traditional monitoring methods nor USA universal soil loss equation is able to predict the correct amount of soil erosion in reality, this study is aimed to explore the characteristics and mechanism of soil erosion and to establish soil erosion coupled model for building a scientific basis to simulate soil erosion and rock desterification in the karst region in question. .The basic approach adopted here includes: (1) to study the characteristics of surface erosion in karst area through runoff plots monitoring in Nanchuan; (2) to explore the proportion of surface and underground leakage on the small scale through three years' monitoring based on paint scheme and piling and measuring the 137Cs content of 5cm layer soil sample in runoff plots; (3)to estimate the loss ratio of surface and underground on the large scale with the ratio method by measuring 137Cs content both in surface soil according to different land use types and in ground river silt at study area ; （4）to calculate the loss ratio of surface and underground on the large scale with the data of both runoff plots and ground sediment monitoring;(5)to build soil erosion coupled model based on the study of the characteristics and mechanism of soil erosion in karst area. .Research results would provide the necessary reference for governing pollution of underground river , afford scientific basis for accurate estimation of surface and subsurface soil erosion and afford reliable protection for governing soil erosion and rock desertification issues and consolidate the scientific basis to prevent water and soil loss for Karst region in general and Three Gorges of Chongqing in particular.

我国西南地区岩溶面积广布且人口众多，导致岩溶地区水土流失严重，石漠化广布。中共中央印发的2011年1号文件中提到"要进一步加强中国西南岩溶地区水土流失治理"，"十二o五"规划中也提到要"加强石漠化综合治理"。治理水土流失、石漠化的前提是弄清楚水土流失量。岩溶地区土壤存在漏失现象，采用传统的方法监测水土流失量不能真实反映水土流失，采用美国通用土壤流失方程计算的土壤侵蚀值与实际流失量相差甚远，因此有必要弄清岩溶地区水土流失特征及机理，建立岩溶地区水土流失耦合模型。.本项目采用径流小区、打桩、划油漆、核示踪技术、地下河泥沙监测等方法，分析岩溶地区水土流失特征、土壤地下漏失特征及地下漏失比例、水土流失机理，建立岩溶地区水土流失耦合模型。.研究意义：为岩溶地区准确计算地表、地下土壤侵蚀量提供科学依据，为正确判定土壤侵蚀强度、治理水土流失和石漠化问题提供有效保障，为防治三峡库区水土流失提供科学依据。

治理水土流失、石漠化的前提是弄清楚水土流失量。岩溶地区土壤存在漏失现象，采用传统的方法监测水土流失量不能真实反映水土流失，采用美国通用土壤流失方程计算的土壤侵蚀值与实际流失量相差甚远，因此有必要弄清岩溶地区水土流失特征及机理，建立岩溶地区水土流失耦合模型。通过研究岩溶槽谷区水土流失特征，得到岩溶地区地表流失量不高；利用137CS、粒度分析，划油漆、打桩等方法得到岩溶槽谷区土壤存在漏失现象，通过土壤有机质表征土壤漏失现象；通过前面的观测研究结果，得到岩溶地区土壤地表流失和地下漏失公式，构建岩溶地区耦合模型，并计算得出岩溶地区土壤地下漏失率不高；运用岩溶槽谷区耦合模型，分析了水土流失强度与环境因子的相关性；找到水土流失与石漠化的内在动因，为进一步防治水土流失和石漠化提供科学依据。项目为治理岩溶地区水土流失，防治石漠化提供科学依据。通过研究发现岩溶槽谷区土壤地下漏失率低至25%及以下，因此岩溶地区土壤地下漏失对三峡库区的泥沙淤积贡献不大。