Laboratory of Water, Hydro-Systems and Agriculture (LEHSA), International Institute for Water and Environmental Engineering (2iE), 01 PO Box 594, Ouagadougou 01, Burkina Faso.
Laboratory of Water, Hydro-Systems and Agriculture (LEHSA), International Institute for Water and Environmental Engineering (2iE), 01 PO Box 594, Ouagadougou 01, Burkina Faso.
Sci Total Environ. 2021 Feb 25;757:143792. doi: 10.1016/j.scitotenv.2020.143792. Epub 2020 Nov 27.
In Sahelian landscapes, land use/land cover (LULC) dynamics and climate variability are already known to affect the water cycle. In its current practice however, hydrological modelling does not account for LULC changes. This issue pertains to rapidly evolving watersheds and might result in critical inaccuracies in the simulated processes. In this study, the Soil and Water Assessment Tool (SWAT) model was used to simulate surface runoff in the small Sahelian watershed of Tougou, which underwent significant LULC changes between 1952 and 2017. Based on rainfall/runoff data acquired from 2004 to 2018, the SWAT model was calibrated under two scenarios: a static land use scenario (SLU) using a single LULC map (in 1999) and a dynamic land use scenario (DLU) integrating 3 LULC maps (1999, 2009 and 2017). The DLU scenario estimated with higher accuracy surface runoff, deep aquifer infiltration and actual evapotranspiration processes. Based on the calibrated parameters, surface runoff was simulated during the historical period 1952-2003 under four scenarios with static LULC maps (in 1952, 1973, 1986 and 1999) opposed to a fifth scenario integrating these LULC maps dynamically. The DLU scenario was found to be more effective at picturing the so-called Sahelian paradox (i.e. the increase in surface runoff despite the decrease in rainfall), reported in the literature for small watersheds in the Sahel. The analysis of variability revealed that fluctuations in surface runoff were both influenced by rainfall and LULC changes. Furthermore, the isolated contributions of climate variability and LULC changes on surface runoff showed that LULC conditions played a dominant role (η = +393.1%) in the runoff increase over climate (η = -297%) during the historical period. These results highlight the importance of accounting for LULC dynamics in hydrological modelling and advocate the development of integrated modelling frameworks for hydrologists and water resource managers.
在萨赫勒景观中，土地利用/土地覆被（LULC）动态和气候变化已经被证实会影响水循环。然而，在当前的实践中，水文模型并没有考虑到 LULC 的变化。这个问题涉及到快速演变的流域，可能会导致模拟过程中出现严重的不准确。在这项研究中，土壤和水评估工具（SWAT）模型被用于模拟 Tougou 这个小型萨赫勒流域的地表径流，该流域在 1952 年至 2017 年间经历了显著的 LULC 变化。基于 2004 年至 2018 年的降雨/径流数据，SWAT 模型在两种情景下进行了校准：一种是使用单一 LULC 地图（1999 年）的静态土地利用情景（SLU），另一种是整合了 3 个 LULC 地图（1999 年、2009 年和 2017 年）的动态土地利用情景（DLU）。DLU 情景估计的地表径流、深层含水层入渗和实际蒸散过程更准确。根据校准后的参数，在历史时期 1952 年至 2003 年，使用静态 LULC 地图（1952 年、1973 年、1986 年和 1999 年）进行了四个情景下的地表径流模拟，而第五个情景则整合了这些 LULC 地图进行动态模拟。研究发现，DLU 情景更能有效地描绘所谓的萨赫勒悖论（即在降雨量减少的情况下地表径流增加），这在萨赫勒地区的小流域文献中有报道。对变异性的分析表明，地表径流的波动既受到降雨的影响，也受到 LULC 变化的影响。此外，气候变异性和 LULC 变化对地表径流的单独贡献表明，在历史时期，LULC 条件对径流增加的主导作用（η=+393.1%）超过了气候的主导作用（η=-297%）。这些结果强调了在水文模型中考虑 LULC 动态的重要性，并主张为水文学家和水资源管理者开发综合建模框架。
