Evaluating Effects of Climate Change and Variability on Snowmelt Runoff Timing and Magnitude in Northern New Mexico

In the mountains of northern New Mexico, potential impacts of climate change include alteration in the amount and timing of runoff of surface water. More than half of the available surface water in New Mexico comes from high elevation watersheds, making it critical to understand discharge trends in order to provide water to sustain the population and economy of New Mexico. Climate change affects temperature and the rate, timing, and form of precipitation that in turn could result in a change in snowmelt timing and flow quantities over the annual hydrograph. Updated and enhanced methods to predict the timing and yield of water from stream basins and the amount of water that can be used for agriculture and municipal use are needed. Here, we examine the use of stream discharge to model temporal and spatial trends of available water. Historical discharge records for two mountain streams in northern New Mexico, the Jemez River and Rio Hondo, were examined for trends in the timing of the start and the end of snowmelt runoff. We also examine trends in the snowmelt season fractional flows (ratio of selected monthly intervals during snowmelt season to total annual flow). Snowmelt start and end days were determined as the day on which the cumulative flow departure from average was at a minimum and maximum, resulting in a hydrograph (rather than discharge) driven metric. Changes in timing and trends were analyzed using statistical methods including correlation testing and regression analysis. Models of snowmelt amount and timing can be used as baseline comparisons through which improved infrastructure for monitoring and modeling climate change impacts on New Mexico’s mountain sources of water can be developed. Detailed sampling of the Jemez and Hondo watersheds through annual hydrological cycles will provide isotopic and hydrochemical data that can assist in hydrograph separation between snowmelt and base flows sustained by deeper groundwater flows. In 2010, a network of state-of-the-art, near-real-time, autonomous water quality sensors was deployed in the Jemez river watershed for detecting rapid changes in surface water and groundwater solute fluxes associated with snowmelt events. We anticipate that the models and analytical tools under development can be coupled with outputs from the monitoring network to provide a basis for more detailed investigations into climate controls on water chemistry, biogeochemical processes, and future impacts from climate change on ecosystems and downstream water users.