Temporal Tendencies of River Discharge of Five Watersheds of Northern Mexico

The watersheds of northern Mexico that encompasses the Rio San Pedro, Sinaloa, Nazas, Aguanaval, San Juan, and San Fernando-Soto La Marina are located within the main mountain ranges of northern Mexico and within the zone of large deserts of the boreal hemisphere. The hydro-climate variations, the management of forest soils and land use changes are shaping the supply and management of water resources. This research project aims to understand whether changes in discharge variables are present in time series data of 172 gauging stations of five watershed of northern Mexico. The Mann-Kendall test and the Sen’s method were used to test for statistical changes in trends or tendencies and the magnitude of change of annual, monthly, monthly standard deviation, daily minimum (baseflow), and daily maximum (peakflow) discharge of the hydrometric stations mentioned above. Results showed that over 40 percent of the gauging stations had statistical significant tendencies in each of the five discharge variables analyzed. Most tendencies had a negative sign indicating a steady reduction of discharge in time. The reduction was, on the average over 5,000 m3 year-1 for annual discharge. Although further research is required to understand the potential sources of variation that explains the negative tendencies of discharge, it can be preliminary attributed to subtle climate changes, and management practices of water and other natural resources.