Groundwater use in the Middle Rio Grande (MRG) has accelerated
recently as the region's population and consequent water demands have increased.
Surface water was historically used for irrigation and its allocation
carefully regulated. Groundwater was historically reserved for domestic uses.
Its allocation was largely unregulated and regarded as separate from and unconnected to river water.

Connection has been observed between groundwater and surface water
in the MRG's riparian forest, known as the bosque (MRGB). Cottonwood and willow are two species of
native riparian phreatophyte known to depend upon the bosque's shallow, unconfined aquifer for successful establishment and survival.
Quantifying the connection between the groundwater and river stage can permit a more realistic and
equitable allocation of the Middle Rio Grande's scarce water between ecological,
agricultural, and domestic users.

We sampled the distance from soil to groundwater at a 30 minute intervals for Water Year 2006 at numerous sites in the MRGB. We entered the data into a relational database and analyzed it using a statistical package that communicates directly with the database (both are Open Source Software (OSS) and freely available). We selected three sites in the MRGB, ranging in location from Albuquerque to Bosque del Apache, for Water Year 2006. We then obtained river stage from the nearest available upstream USGS river gage.
We calculated a simple linear regression at each site using a response variable of daily mean groundwater level and a predictor variable of daily mean river stage. At each site we found a strong, positive linear relationship at high river stage
and poor relationship at low river stage. In addition, we interpreted the
response curves at each site and found evidence of
hysteresis at the north-most site and flooding at the south-most site.

These findings suggest that groundwater consumption and recharge in the
MRGB are connected to surface water, and might be accounted for in regional surface water budgets.