DROUGHT ASSESSMENT USING REMOTE SENSING IN THE ALLENDE - PIEDRAS NEGRAS TRANSBOUNDARY AQUIFER

The Allende-Piedras Negras (APN) aquifer is located between the state of Texas (USA) and the state of Coahuila (Mexico). The Rio Grande/Rio Bravo crosses the aquifer acting as a natural and political divide between both countries. Besides, the area had a gap identified by previous studies where the absence of an aquifer assignment was notorious; also, these studies were developed at the local level but not covering the entire gap. The main purpose of this study is the identification of drought periods in the APN aquifer from remote sensing data (Precipitation, temperature, change in total water storage-TWS, lake height variations) from July 2008 to July 2016, and compare the different parameters to identify possible correlations amongst them. Also, a validation of the data obtained with previous studies reporting drought periods in the APN aquifer is crucial to verify the usefulness of the methodology followed in this study.

The comparison of precipitation, temperature, change in TWS, and lake height variations allow a simple and easy identification of past droughts and wet periods, as well as the analysis of the surface water events and possible relationships with groundwater masses, which were collected using indirect methods. When TWS is used together with groundwater models, it is possible to follow a similar trend between them; however, the discrepancies to estimate a water table change with TWS make necessary to separate soil moisture and surface water from the satellite readings, which implies extra calculations not performed in this study. Another important finding is that the temperature analysis for drought periods is commonly focused on summer seasons, but warmer winters need extra analysis too because these events may indicate severe drought conditions on the following summer.

This comparison from remote sensing data could also be applied in other aquifers that straddle the border. The expected impact of this study is that it will motivate future drought analysis studies on other poorly studied aquifers along the border between USA-Mexico and provide the first assessments for potential joint aquifer management in the region.