José NávarLiliana LizárragaMendiola
In Mexico?s northern dry land watersheds, society is increasingly concerned about seasonal and longtermriver flow variability as a result of potential climate change because industrial, public, domestic, and agricultural sectors all require reliable water supplies. The aim of this research was to break river flow components and to quantify temporal patterns of 172 time series of five of Mexico?s northern rivers. The Rios San Pedro, Sinaloa, NazasAguanaval, San Juan, and San FernandoSoto La Marina begin in the main mountain ranges, Sierra Madre Occidental and Oriental, flowing through the Plains of the Pacific Ocean, Gulf of Mexico and Central Plateau providing the region with more than 90% of all conventional water supplies. The Rora computer program separated baseand direct from daily total flow. The MannKendall analysis and Sen S method tested for temporal tendencies and magnitude changes of annual, monthly, monthly standard deviation, daily minimum, and daily maximum discharge for total, direct and base flow. Results showed base and direct flow are in equilibrium for most rivers but over 40% of the gauging stations had statistically significant temporal patterns in each of five river flow variables analyzed. Over 26% of the gauging stations showed a steady totaldischarge decline over time. Although further research is required to quantitatively isolate the potential sources of variation that explains temporal tendencies, they can be preliminary attributed to climate variability coupled with management practices of natural resources. Potential climate change cannot be ruled out as a main driver of this hydrologic change.