Potential Correlations of Historical Otowi Gage Sediment and Water Flows to Upstream Groundwater Management Practices

The Otowi Gage along the Rio Grande in north-central New Mexico has been in continuous operation since 1895 and sediment transport has been monitored there since 1955. This streamflow record has been relied upon by the Rio Grande Compact signatories Colorado, New Mexico, and Texas as an interstate water administration decision metric since the 1940s. As with most western water courses, the highs and lows of sediment discharge have tracked closely with the highs and lows of water discharge past the gage over the extended period of co-measurement. However, an anomalous pattern of low sediment loads was reported at the Otowi Gage in the 1980s, even as monthly streamflow readings were historically high over that same decade. This paper combs through the primary data sets in an independent evaluation of the pattern. Among other historical sources, we review the San Juan Chama diversion project and the nearby groundwater augmentation program known as the San Luis Valley Project, in the Upper Rio Grande watershed, both which came online near the beginning of the 1980s. Following a hydrography review of the Upper Rio Grande above Otowi, we proceed to explore the underlying aquifer basins via literature sources. From that information baseline, we develop first-order correlation and spectral processing of the Otowi Gage time series data. We work from interpretations of those time series to produce a simplified set of coupled groundwater, surface water, and sediment flow realizations through our customized version of the Hydrological Simulation Program. We discuss our results in relation to other conceptual models, and we close with perspectives of future information development which may help in the continual challenge to address related questions of groundwater flows, surface water flows, and sediment transport faced by contemporary water resource managers.