HESSD Hydrology and Earth System Sciences Discussions HESSD Hydrol. Earth Syst. Sci. Discuss. 1812-2116 Göttingen, Germany 10.5194/hessd-11-9863-2014 Reducing the basin vulnerability by land management practices under past and future climate: a case study of the Nam Ou River Basin, Lao PDR Maharjan M. 1 Babel M. S. 1 Maskey S. 2 Water Engineering and Management, Asian Institute of Technology, P.O. Box 4 Klong Luang, Pathumthani 12120, Thailand Department of Water Science and Engineering, UNESCO-IHE Institute for Water Education, P.O. Box 3015, 261DA Delft, the Netherlands 21 08 2014 11 8 9863 9905 Copyright: © 2014 M. Maharjan et al. 2014 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://hess.copernicus.org/preprints/11/9863/2014/hessd-11-9863-2014.html The full text article is available as a PDF file from https://hess.copernicus.org/preprints/11/9863/2014/hessd-11-9863-2014.pdf

This research evaluates different land management practices for the Nam Ou River Basin in Northern Laos for reducing vulnerability of the basin due to erosion and sediment yield under existing and future climate conditions. We use climate projection data (precipitation and temperature) from three general circulation models (GCMs) for three greenhouse gas emission scenarios (GHGES), namely B1, A1B and A2 and three future periods, namely 2011–2030, 2046–2065 and 2080–2099. These large resolution GCM data are downscaled using the Long Ashton Research Station-Weather Generator (LARS-WG). The Soil and Water Assessment Tool (SWAT), which is a process based hydrological model, is used to simulate discharge and sediment yield and a threshold value of annual sediment yield is applied to identify vulnerable sub-basins. Results show that the change in the annual precipitation is expected to be between −7.60 to 2.64% in 2011–2030, −8.98 to 11.85% in 2046–2065, and −11.04 to 25.84% in 2080–2099. In the meantime, the changes in mean monthly temperature vary from 0.3 to 1.3 °C in the 2011–2030, 1.3 to 2.9 °C in the 2046–2065 and 1.9 to 4.9 °C in the 2080–2099. Five sub-basins are identified vulnerable (critical) under the current climate. Our results show that terracing is the most effective land management practice to reduce sediment yield in these sub-basins followed by strip-cropping and filter strip. Appropriate land management practices applied under future climate scenarios show significant reduction in sediment yield (i.e. up to the tolerance limit) except for some sub-basins. In these exceptional sub-basins, designing an optimum combination of management practices is essential to reduce the vulnerability of the basin.

 103807 References Arnold, J. G., Williams, J. R., and Maidment, D. R.: Continuous-time water and sediment-routing model for large basins, J. Hydraul. Eng.-ASCE, 121, 171–183, 1995. Babel, M. S., Shrestha, B., and Perret, S.: Hydrological impact of biofuel production: a case study of the KhlongPhlo Watershed in Thailand, Agric. Water Manage., 101, 8–26, 2011. Bates, B. C., Kundzewicz, Z. W., Wu, S., and Palutikof, J. P. (Eds.): Climate change and water: Technical Paper of the Intergovernmental Panel on Climate Change, IPCC Secretariat, Geneva, 210 pp., 2008. Behera, S. and Panda, R. K.: Evaluation of management alternatives for an agricultural watershed in a sub-humid subtropical region using a physical process based model, Agric. Ecosyst. Environ., 113, 62–72, 2006. Betrie, G. D., Mohamed, Y. A., van Griensven, A., and Srinivasan, R.: Sediment management modelling in the Blue Nile Basin using SWAT model, Hydrol. Earth Syst. Sci., 15, 807–818, <a href="http://dx.doi.org/10.5194/hess-15-807-2011">https://doi.org/10.5194/hess-15-807-2011</a>, 2011. Bieger, K., Hörmann, G., and Fohrer, N.: Simulation of streamflow and sediment with the Soil and Water Assessment Tool in a Data Scarce Catchment in the Three Gorges Region, China, J. Environ. Qual., 43, 37–45, <a href="http://dx.doi.org/10.2134/jeq2011.0383">https://doi.org/10.2134/jeq2011.0383</a>, 2012. Bracmort, K., Arabi, M., Frankenberger, J., Engel, B., and Arnold, J. R.: Modeling long-term water quality impact of structural BMPs, T. ASABE, 49, 367–374, 2006. Chakraborti, A. K.: Sediment yield prediction and prioritisation of watersheds using remote sensing data, in: Proceedings of the 12th Asian Conference on Remote Sensing, 3 October–5 November, Singapore, Q-3-1–Q-3-6, 1991. Chen, J., Brissette, F. P., Poulin, A., and Leconte, R.: Overall uncertainty study of the hydrological impacts of climate change for a Canadian watershed, Water Resour. Res., 47, W12509, <a href="http://dx.doi.org/10.1029/2011WR010602">https://doi.org/10.1029/2011WR010602</a>, 2011. Christensen, N. S., Wood, A. W., Lettenmaier, D. P., and Palmer, R. N.: The effects of climate change on the hydrology and water resources of the Colorado River Basin, Climatic Change, 62, 337–363, 2004. Di Baldassarre, G., Elshamy, M., van Griensven, A., Soliman, E., Kigobe, M., Ndomba, P., Mutemi, J., Mutua, F., Moges, S., Xuan, Y., Solomatine, D., and Uhlenbrook, S.: Future hydrology and climate in the River Nile basin: a review, Hydrolog. Sci. J., 56, 199–211, 2011. Feng, X., Wang, Y., Chen, L., Fu, B., and Bai, G.: Modelling soil erosion and its response to land-use change in hilly catchments of the Chinese Loess Plateau, Geomorphology, 118, 239–248, 2010. Fuchs, H. J.: Data availability for studies on effects of land-cover changes on water yield, sediment and nutrients load at catchments of the Lower Mekong Basin, Working Paper 09, MRC-GTZ Cooperation Programme, Göttingen, 2004. Gao, P., Geissen, V., Ritsema, C. J., Mu, X.-M., and Wang, F.: Impact of climate change and anthropogenic activities on stream flow and sediment discharge in the Wei River basin, China, Hydrol. Earth Syst. Sci., 17, 961–972, <a href="http://dx.doi.org/10.5194/hess-17-961-2013">https://doi.org/10.5194/hess-17-961-2013</a>, 2013. Giri, S., Nejadhashemi, A. P., and Woznicki, S. A.: Evaluation of targeting methods for implementation of best management practices in the Saginaw River Watershed, J. Environ. Manage., 103, 24–40, 2012. Gupta, A., Hock, L., and Xiaojing, H.: Evaluation of part of the Mekong River using satellite imagery, Geomorphology, 44, 221–239, 2002. Haan, C. T., Barfield, B. J., and Hayes, J. C.: Design hydrology and sedimentology for small catchments, Academic Press, New York, 1994. Hardy, R. L.: Multiquadric equations of topology and other irregular surface, J. Geophys. Res., 76, 1905–1915, 1971. Hoanh, C. T., Jirayoot, K., Lacombe, G., and Srinetr, V.: Impact of climate change and development on Mekong flow regime, First Assessment-2009, MRC Technical paper No. 29. Mekong River Commission, Vientiane, Lao PDR, 2010. Hovius, N.: Controls on sediment supply by large rivers, in: Relative role of Ecstasy, Climate, and Tectonics in Continental Rocks, edited by: Shanley, K. W. and McCabe, P. J., SEPM Special Publication, USA, 59, 3–16, 1998. Jain, S. K., Tyagi, J., and Singh, V.: Simulation of runoff and sediment yield for a Himalayan watershed using SWAT model, J. Water Resour. Prot., 2, 267–281, 2010. Janeau, J. L., Bricquet, J. P., Planchon, O., and Valentin, C.: Soil crusting and infiltration on very steep slopes in northern Thailand, Eur. J. Soil Sci., 5, 543–553, 2003. Kingston, D. G., Thompson, J. R., and Kite, G.: Uncertainty in climate change projections of discharge for the Mekong River Basin, Hydrol. Earth Syst. Sci., 15, 1459–1471, <a href="http://dx.doi.org/10.5194/hess-15-1459-2011">https://doi.org/10.5194/hess-15-1459-2011</a>, 2011. Labat, D., Godd, Y., Probst, J. L., and Guyot, J. L.: Evidence for global runoff increase related to climate warming, Adv. Water Resour., 27, 631–642, 2004. Laurent, F. and Ruelland, D.: Assessing impacts of alternative land use and agricultural practices on nitrate pollution at the catchment scale, J. Hydrol., 409, 440–450, 2011. Lee, M., Park, G., Park, M., Park, J., Lee, J., and Kim, S.: Evaluation of non-point source pollution reduction by applying Best Management Practices using a SWAT model and QuickBird high resolution satellite imagery, J. Environ. Sci., 22, 826–833, 2010. Li, Y., Chen, B.-M., Wang, Z.-G., and Peng, S.-L.: Effects of temperature change on water discharge, and sediment and nutrient loading in the lower Pearl River basin based on SWAT modeling, Hydrolog. Sci. J., 56, 68–83, 2011. Lu, X. X. and Siew, R. Y.: Water discharge and sediment flux changes over the past decades in the Lower Mekong River: possible impacts of the Chinese dams, Hydrol. Earth Syst. Sci., 10, 181–195, <a href="http://dx.doi.org/10.5194/hess-10-181-2006">https://doi.org/10.5194/hess-10-181-2006</a>, 2006. Lu, X. X., Ran, L. S., Liu, S., Jiang, T., Zhang, S. R., and Wang, J. J.: Sediment loads response to climate change: a preliminary study of eight large Chinese rivers, Int. J. Sediment Res., 28, 1–14, 2013. Maeda, E. E., Pellikka, P. K. E., Siljander, M., and Clark, B. J. F.: Potential impacts of agricultural expansion and climate change on soil erosion in the Eastern Arc Mountains of Kenya, Geomorphology, 123, 279–289, 2010. Maharjan, M.: Impact assessment of climate change and land management practices on sediment yield: a case study in the Nam Ou river basin, Lao PDR, (Masters thesis study No. WM-12-13, Asian Institute of Technology, 2012), Bangkok: Asian Institute of Technology, 2012. Minville, M., Brissette, F., and Leconte, R.: Uncertainty of the impact of climate change on the hydrology of a Nordic watershed, J. Hydrol., 358, 70–83, 2008. Mullan, D.: Soil erosion under the impacts of future climate change: assessing the statistical significance of future changes and the potential on-site and off-site problems, Catena, 109, 234–246, 2013. Nash, J. E. and Sutcliffe, J. V.: River flow forecasting through conceptual models, Part I – a discussion of principles, J. Hydrol., 10, 282–290, 1970. Neitsch, S. L., Arnold, J. G., Kiniry, J. R., and Williams, J. R.: Soil and Water Assessment Tool Theoretical Documentation Version 2009, Texas Water Resources Institute, College Station, Texas, USA, 2009. Nunes, J. P. and Nearing, M. A.: Modelling impacts of climatic change, in: Handbook of Erosion Modelling, edietd by: Morgan, R. P. C. and Nearing, M. A., Wiley-Blackwell, Oxford, 289–312, 2011. Nunes, J. P., Seixas, J., Keizer, J. J., and Ferreira, A. J. D.: Sensitivity of runoff and soil erosion to climate change in two Mediterranean watersheds, Part II: Assessing impacts from changes in storm rainfall, soil moisture and vegetation cover, Hydrol. Process., 23, 1212–1220, 2009. O'Neal, M. R., Nearing, M. A., Vining, R. C., Southworth, J., and Pfeifer, R. A.: Climate change impacts on soil erosion in Midwest United States with changes in crop management, Catena, 61, 165–184, 2005. Phan, D. B., Wu, C. C., and Hsieh, S. C.: Impact of climate change on stream discharge and sediment yield in Northern Viet Nam, Water Resour., 38, 827–836, 2011. Phomcha, P., Wirojanagud, P., Vangpaisal, T., and Thaveevouthti, T.: Predicting sediment discharge in an agricultural watershed: a case study of the Lam Sonthi watershed, Thailand, Science Asia, 37, 43–50, 2011. Qui, L. J., Zheng, F. L., and Yin, R. S.: SWAT-based runoff and sediment simulation in a small watershed, the loessial hilly-gullied region of China: capabilities and challenges, Int. J. Sediment Res., 27, 226–234, 2012. Racsko, P., Szeidl, L., and Semenov, M. A.: A serial approach to local stochastic weather models, Ecol. Model., 57, 27–41, 1991. Reungsang, P., Kanwar, R. S., and Srisuk, K.: Application of SWAT model in simulating stream flow for the Chi River Subbasin II in Northeast Thailand, Trend Res. Sci. Technol., 2, 23–28, 2010. Roberts, T.: Downstream ecological implications of China's Lancang Hydropower and Mekong Navigation Project, International Rivers Network, Berkeley, USA, 2001. Rossi, C. G., Srinivasan, R., Jirayoot, K., Duc, T. L., Souvannabouth, P., Binh, N., and Gassman, P. W.: Hydrologic evaluation of the Lower Mekong River Basin with the soil and water assessment tool model, Int. Agr. Eng. J., 18, 1–13, 2009. SCS (Soil Conservation Service) Hydrology: National Engineering Handbook, Section 4, USDA Natural Resources Conservation Society, USA, 1972. Semenov, M. and Stratonovitch, P.: Use of multi-model ensembles from global climate models for assessment of climate change impacts, Clim. Res., 41, 1–14, 2010. Setegn, S. G., Dargahi, B., Srinivasan, R., and Melesse, A. M.: Modeling of sediment yield from Anjeni-Gauged watershed, Ethiopia using SWAT model, J. Am. Water Resour. As., 46, 514–526, 2010. Shrestha, B., Babel, M. S., Maskey, S., van Griensven, A., Uhlenbrook, S., Green, A., and Akkharath, I.: Impact of climate change on sediment yield in the Mekong River basin: a case study of the Nam Ou basin, Lao PDR, Hydrol. Earth Syst. Sci., 17, 1–20, <a href="http://dx.doi.org/10.5194/hess-17-1-2013">https://doi.org/10.5194/hess-17-1-2013</a>, 2013. Teng, J., Vaze, J., Chiew, F. H. S., Wang, B., and Perraud, J. M.: Estimating the relative uncertainties sourced from GCMs and hydrological models in modeling climate change impact on runoff, J. Hydrometeorol., 13, 122–139, 2012. Ullrich, A. and Volk, M.: Application of the Soil and Water Assessment Tool (SWAT) to predict the impact of alternative management practices on water quality and quantity, Agric. Water Manage., 96, 1207–1217, 2009. Van liew, M. W., Veith, T. L., Bosch, D. D., and Arnold, J. G.: Suitability of SWAT for the conservation effects assessment project: a comparison on the USDA-ARS experimental watersheds, J. Hydrol. Eng., 12, 173–189, 2007. Walling, D. E.: Measuring sediment yield from river basin, in: Soil Erosion Research Methods, edited by: Lal, R., Soil and Water Conservation Society, Ankeny, Iowa, 11, 39–80, 1994. Wang, F., Mu, X., Hessel, R., Zhang, W., Ritsema, C. J., and Li, R.: Runoff and Sediment load of the Yan River, China: changes over the last 60 yr, Hydrol. Earth Syst. Sci., 17, 2515–2527, <a href="http://dx.doi.org/10.5194/hess-17-2515-2013">https://doi.org/10.5194/hess-17-2515-2013</a>, 2013. Wang, J. J., Lu, X. X., and Kummu, M.: Sediment load estimates and variations in the Lower Mekong River, River Res. Appl., 27, 33–46, 2011. Williams, J. R.: Flood routing with variable travel time or variable storage coefficients, Trans. ASAE, 12, 100–103, 1969. Williams, J. R.: Sediment routing for agricultural watersheds, Water Resour. Bull., 11, 965–974, 1975. Wischmeier, W. H. and Smith, D. D.: Predicting Rainfall Losses: a Guide to Conservation Planning, USDA Agricultural Handbook No. 537, US Gov. Print. Office, Washington, DC, 1978. Xu, H., Taylor, R. G., and Xu, Y.: Quantifying uncertainty in the impacts of climate change on river discharge in sub-catchments of the Yangtze and Yellow River Basins, China, Hydrol. Earth Syst. Sci., 15, 333–344, <a href="http://dx.doi.org/10.5194/hess-15-333-2011">https://doi.org/10.5194/hess-15-333-2011</a>, 2011. Yang, D., Kanae, S., Oki, T., Koike, T., and Musiake, K.: Global potential soil erosion with reference to land use and climate changes, Hydrol. Process., 17, 2913–2928, 2003. You, L. Y.: A study on temporal changes of river sedimentation in Lancang River Basin, Scientia Geographica Sinica, 54, 93–100, 1999. Zhang, X. C.: A comparison of explicit and implicit spatial downscaling of GCM output for soil erosion and crop production assessments, Climatic Change, 84, 337–363, 2007. Zhang, X. C. and Nearing, M. A.: Impact of climate change on soil erosion, runoff, and wheat productivity in Central Oklahoma, Catena, 61, 185–195, 2005. Zhang, X. and Zhang, M.: Modeling effectiveness of agricultural BMPs to reduce sediment load and organophosphate pesticides in surface runoff, Sci. Total Environ., 409, 1949–1958, 2011. Zhang, X., Srinivasan, R., and Hao, F.: Predicting hydrologic response to climate change on the Luohe River Basin using the SWAT model, Am. Soc. Agr. Biol. Eng., 50, 901–910, 2007. Zhu, Y. M., Lu, X. X., and Zhou, Y.: Sediment flux sensitivity to climate change: a case study in the Longchuanjiang catchment of the upper Yangtze River, China, Global Planet. Change, 60, 429–442, 2008.