Water
"...with scarce and scattered water sources, the Monument is an outstanding biological resource..."
Presidential Proclamation, September 1996

Groundwater Discharge from the Navajo Sandstone in the Escalante Basin
In partnership with USGS Water Resources Division, Utah Division of Water Rights, University of Utah, Northern Arizona University, and University of Nevada - Las Vegas

In a region characterized by shallow soils and sparse annual precipitation, perennial streamflow is limited to areas of groundwater discharge. Of the several water-bearing sedimentary units within the Monument, the most significant is the Jurassic Navajo Sandstone (Figure 4). This continuous, well-sorted eolian sandstone provides large quantities of high quality water. Values for the thickness (1,500 to 2,250 feet), saturated thickness (100 to 2,000 feet), hydraulic conductivity (0.1 to >3 feet/day), and transmissivity (100 to >2000 feet2/day) of this important regional aquifer are at or near their maximum within GSENM (Blanchard, 1987; Freethey and Cordy).

One of the most compelling – yet poorly understood – expressions of discharge from the Navajo occurs in the headwaters of the Escalante River. Over a distance of 20 miles, five tributaries (Pine, Mamie, Sand, Calf, and Boulder/Deer Creeks) enter the river and provide more than 95% of the baseflow for the entire 80-mile length of the river (Figure 5) (Wilberg and Stolp, 2005). High rates of groundwater discharge in this area are presumed to reflect the combination of thick Navajo sandstone units and local recharge derived from nearby high elevation terrain composed of Navajo sandstone overlain by fractured basalt and volcanic colluvium. Previous researchers have hypothesized that the incised tributary canyons act as groundwater ‘drains’ that intercept groundwater originating from Boulder Mountain before it reaches the Escalante River (Wilberg and Stolp, 2005). These researchers also suggest that baseflows in Calf Creek may be derived from topographically higher reaches of Sand Creek and/or Boulder Creek.

The locations and magnitudes of groundwater discharges into these tributaries have never been quantified. Except for Calf Creek, baseflows in these streams are a mixture of discharge from volcanic strata and the Navajo, and flow accretions occur both upstream and within the Monument. Given the ecological and social importance of the Escalante River, it is important to understand the origin of its baseflows. The objectives of this ongoing research effort are to:

1. Quantify rates of groundwater discharge to these streams within the Monument;
2. Document temporal variability in groundwater discharge within and upstream from the Monument;
3. Describe source areas, flow paths, and travel times for select springs.


While it is too early to draw conclusions from this work, it is apparent that substantial baseflow accretions from the Navajo sandstone occur with the Monument. Tributary groundwater accretions within the Monument account for perhaps 20 to 40% of Escalante River baseflows. Inflows occur primarily in the tributary systems, with direct groundwater discharge to the River limited to hanging gardens (Figure 7). Interannual variability in these flows appears to be relatively low.

Ongoing field work will attempt to better quantify the magnitude and range of variability of groundwater accretions, to improve our understanding of groundwater flows paths and groundwater exchange between surface water systems, and to relate groundwater-surface water dynamics to ecological processes (e.g., accounting for evapotranspiration losses to estimate water requirements of riparian woodlands).

Spatial Trends in Water Quality in the Paria River and Sheep Creek
Contact Information: Dr. Dave Kreamer, University of Nevada-Las Vegas
Contact Information: Jamie Harris, University of Nevada-Las Vegas

The Paria River exceeds EPA limits for salinity, chloride and total dissolved solids. Water quality was sampled at six locations in October 2002 to describe longitudinal trends and determine whether water quality conditions were correlated with lithologic characteristics (Figure 8). Major ion analyses suggest that ion abundances are highest at points located within and downstream from reaches that flow through shale units (Tropic and Chinle) and are lowest at sample points influenced by groundwater discharge from the Navajo sandstone. These data indicate that dissolved ion concentrations observed during baseflows reflect ‘background’ conditions.

Sheep Creek, an ephemeral stream, is a tributary to the Paria River. This study characterized the water chemistry of springs (groundwater) and surface water in the Sheep Creek system, based on samples collected at five locations during fall 2002 and spring 2003.

Major ion analyses were used to examine geochemical trends (Figure 9). Preliminary results indicate increasing mineralization with distance downstream. Throughout Sheep Creek, groundwater generally has higher constituent values than the surface water. Ion concentrations are highest in springs discharging from the Straight Cliffs, Entrada, and Carmel formations. Samples in Sheep Creek above the Paria River have significantly lower ion levels, reflecting the contribution of water from the Navajo aquifer. The Sheep Creek site, which is the only site with flowing surface water above the spring inflow, has the most noticeable seasonal fluctuation in surface water chemisty.