Assessment of land cover change effect on the San Juan River watershed hydrology in Nuevo Leon, Mexico

The San Juan River is a part of the Rio Grande/Bravo watershed in the Mexican territory. For many years the San Juan River watershed has been altered by deforestation, which is related to agricultural and urban development. Deforestation can lead to changes in water availability in the watershed. A computer model (Soil and Water Assessment Tool) was used to relate physical characteristics such as soil type, rainfall and land cover type with the water balance of the watershed. The use of the computer was based on the lack of internal gauge stations data in the watershed. There is data from one station at the watershed outlet. However, the computer model allows to get results for specific areas of the watershed. Land cover data from year 1974, 1998 was available for the assessment. Also an estimated land cover map was created for year 2020 considering the growth of urban areas. Modeling results show a significant relation between land cover change and water flows behavior and how small changes in areas of the watershed can produce considerable changes in water flow, i.e. a increase of 19% of the size of urban areas caused an increase of 64% in the surface runoff in the Urban Areas region of the watershed. Model flow results from year 1974, 1998 and 2020 were compared to assess the effect of land cover change on the hydrological processes of the watershed.