Water-borne Soil Erosion Assessment in Rwanda using RUSLE Model
文献类型：学位论文
| 作者 | JEAN DE DIEU NAMBAJIMANA |
| 答辩日期 | 2020 |
| 授予单位 | 中国科学院大学 |
| 授予地点 | 北京 |
| 导师 | 贺秀斌 ; 周继 |
| 关键词 | 水土流失 土地利用 RUSLE 水土保持 卢旺达 |
| 学位名称 | 硕士 |
| 学位专业 | 土壤学 |
| 其他题名 | 基于RUSLE 模型的卢旺达土壤侵蚀评价 |
| 英文摘要 | Soil erosion by water has become a serious threat to food security and environment worldwide. In Rwanda, soil loss due to erosion is leading to water quality deterioration and decline in agricultural productivity. Despite a number of studies previously conducted in Rwanda, with most focusing on a particular region or land use types, temporal distribution of soil erosion by water has not been adequately investigated at a national scale. Moreover, the impacts of land use change on soil erosion by water have not been documented. Therefore, the main objective of this study was to assess soil erosion by water in Rwanda in the year of 2000, 2015 and 2018. A GIS-based Revised Universal Soil Loss Equation (RUSLE) model combined with remote sensing technique was applied to estimate soil erosion rates at a 30 × 30 m cell grid. Geospatial data on precipitation, soil properties, topography, MODIS NDVI, land use and management were used to calculate the model input factors (rainfall erosivity (R), soil erodibility (K), slope length and steepness (LS), cover management (C) and support practice (P)). The land use maps of Rwanda in 2000, 2015 and 2018 were used to separate the area covered by erosion-prone lands with non-erodible ones. The mean annual soil erosion rates have been estimated in 2000, 2015 and 2018. The mean monthly and seasonal soil erosion rates have further been calculated in 2018. Based on the above theoretical and numerical analyses, the main results are as follows: (1) Cropland covered 49.4% (1,125,810 ha) of the total erosion-prone lands in 2000, increased to 59.5% (1,395,340 ha) in 2018. On contrary, forestland accounting for 32.8% (747,500 ha) in 2000, decreased to 19.2% (451,430 ha) in 2018. (2) The average annual soil erosion rates were 48.6 t haˉ1 yˉ1, 39.2 t haˉ1 yˉ1 and 44.6 t haˉ1 yˉ1 in 2000, 2015 and 2018, respectively, resulting in total nationwide losses of approximately 110, 89 and 104 million tons. In 2018，April had the highest monthly soil erosion rate of 6.7 t haˉ1 monthˉ1，while the lowest average monthly soil erosion rate of 0.8 t haˉ1 monthˉ1 had been observed in June. About 39.5% of the average annual soil erosion rate occurred in the short rainy season from September to December in 2018. (3) Forestland experienced the mean soil erosion rate of 93.9 t haˉ1 yˉ1 in 2000, increased to 109.2 t haˉ1 yˉ1 in 2015 and 113.3 t haˉ1 yˉ1 in 2018. This suggests that forestland experienced an increase in mean soil erosion rate by 17.1% over the last 18 years (2000-2018). On the other hand, the mean soil erosion rate for cropland was 20.3 t haˉ1 yˉ1 in 2000, 14.6 t haˉ1 yˉ1 and 16.6 t haˉ1 yˉ1 in 2018, suggesting a decline in mean soil erosion rate by 18.2% from 2000 to 2018. (4) Since investing in soil conservation practices may be constrained by the socio-economic capacity of the local community, socio-economic factors can indirectly exacerbate soil erosion. In this context, an attempt has been made to identify the embedded driving forces of soil erosion in Rwanda. Therefore, in this study, survey data provided by the National Institute of Statistics of Rwanda (NISR) was used to correlate the rate of poverty, extreme poverty and household using chemical fertilizers with the districts’ mean soil erosion rates in 2015. Pearson’s correlation showed that the mean erosion rate was related to poverty (r = 0.45, p = 0.013), increased use of chemical fertilizers (r = 0.77, p = 0.005) which explains the ongoing over-cultivation practice, and significantly correlated with extreme poverty (r = 0.77, p = 0.000). (5) The soil conservation scenario analysis for Rwanda’s cropland in 2015 showed that terracing could reduce the soil erosion rates from 14.6 t haˉ1 yˉ1 to 11.7 t haˉ1 yˉ1. However, lands with strip-cropping and contouring measures have higher soil erosion rates than the mean soil erosion rate occurred in cropland in 2015. |
| 语种 | 英语 |
| 页码 | 101 |
| 源URL | [http://ir.imde.ac.cn/handle/131551/54996]  |
| 专题 | 成都山地灾害与环境研究所_山地表生过程与生态调控重点实验室 |
| 作者单位 | 中国科学院成都山地灾害与环境研究所 |
| 推荐引用方式 GB/T 7714 | JEAN DE DIEU NAMBAJIMANA. Water-borne Soil Erosion Assessment in Rwanda using RUSLE Model[D]. 北京. 中国科学院大学. 2020. |
入库方式： OAI收割
来源：成都山地灾害与环境研究所
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