[1] Diurnal temperature fluctuations of surface water, as result of solar heating, function as a tracer that continuously exchanges energy between streams, streambed sediments, and discharging groundwater. Analytical solutions exist to estimate discharge by extracting the amplitude ratio between pairs of subsurface temperature time series measurements. The research presented here adds to the expanding body of heat tracing literature by applying the amplitude-shift time series discharge estimation method to pairs of distributed temperature sensor (DTS) fiber-optic cables. A pair of DTS fiber-optic cables is placed in an experimental streambed, one over the other, with a small vertical separation to measure continues heat-based vertical streambed fluxes along the entire length of cable, thus eliminating a long series of point measurements. This study utilized time series data from synthetic data sets, modeled numerically using COMSOL Multiphysics, and physical data sets, modeled in a 10 m long sandbox model to assess the viability of this new distributed flux quantification method. Discharge estimated with spatially averaged temperature data are accurately approximated where groundwater flow is uniform and the temperature signal is constant at the streambed surface. Error is introduced where focused groundwater discharge exists, resulting in temperature profiles that vary laterally throughout the streambed. Spatial averaging inherent to DTS data results in dampening of flux measurements over focused discharge zones, as temperature is averaged as a result of the measurement technique. This leads to underestimating peak flux at localized discharge zones and overestimating discharge measurements away from these locations. The spatial integration of the DTS as well as the sampling interval and cable position can lead to error in calculated groundwater fluxes. Results demonstrate the potential advantages and disadvantages of using paired fiber-optic cables to quantify high-resolution groundwater discharge to streams at the reach scale.Citation: Mamer, E. A., and C. S. Lowry (2013), Locating and quantifying spatially distributed groundwater/surface water interactions using temperature signals with paired fiber-optic cables, Water Resour. Res., 49,[7670][7671][7672][7673][7674][7675][7676][7677][7678][7679][7680]
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Here, we summarize our assessment of the impact of unconventional oil and gas exploration and development on groundwater supply sustainability in the San Juan Basin (SJB). The measurement of actual water use in the SJB is difficult, so we tackle this problem using three indirect approaches. First, we evaluate the amount of groundwater that could be used by the petroleum industry in the basin by tabulating the water rights/permits that have been allocated to a variety of stakeholders by the Office of the State Engineer. The largest allocations in the SJB are assigned to mining (coal and uranium, 31.1 %), domestic users and municipalities (28.2%), and food production (24.7%). The petroleum industry owns 6.3% of the groundwater rights, totalling ca. 6674 acre-ft/year (afy). Second, using data from the Oil Conservation Division, we tracked the amount of water reportedly used in hydraulic fracturing of both vertical and horizontal oil and gas wells since 2005. Vertical wells drilled into the Mesaverde Group, Gallup Sandstone, and the Dakota Sandstone account for 83% of hydraulically fractured completions since 2005. Mesaverde Group (Cliff House Sandstone, Menefee Formation, Point Lookout Sandstone) vertical wells averaged 150,000 gallons/well (0.46 acre-ft (af)), vertical Gallup wells averaged 207,000 gallons/well (0.63 af) and vertical Dakota wells used 105,000 gallons/well (0.33 af). The water usage for horizontal wells in the SJB averages 3.13 af/well. Operators in the SJB are using produced water, foam, and nitrogen as hydraulic fracturing agents to reduce water use. Third, we used formation top data from scout cards and well logs to create structure contour and isopach maps of the ten major aquifers in the San Juan Basin. The volume of material in each aquifer, including rock, fluids, and gas, is estimated from the structure contour and isopach maps in ArcGIS using two methods. We then calculate the volume of material above a depth of 2,500 ft below the ground surface (bgs) in the each unit, which is in the accessible part of each aquifer that tends to hold fresh water (<1,000 mg/L TDS). Finally, we estimate the amount of groundwater in storage in the shallow part of each aquifer. For estimated specific storage values of 1.40 to 1.96 x 10 -6 /m, the maximum volume of pre-development water in the shallow portions of confined aquifers <2500 bgs was ~3.25 million acre-ft; this estimate does not include Quaternary aquifers. The maximum amount of water in the San Jose and Nacimiento formations is 83 million acre-ft assuming a specific yield of 0.05 and unconfined conditions, and was 1.21 million acre-ft (pre-development) if the aquifer is assumed to be confined. We calculate that at least 4.5 million acre-ft of groundwater was stored in the accessible parts of the major aquifers prior to the development of groundwater resources in the San Juan Basin. These calculations are approximations due to the inherent stratigraphic complexity of the aquifers and must be used with care. Complications include discontinuity of unit...
In response to increasing needs to understand the water budget of New Mexico, we have constructed estimates of historical groundwater storage change in the shallow (less than 1000 ft), unconfined alluvial aquifers of the state. Shallow, unconfined alluvial aquifers in New Mexico form the major groundwater reservoirs in many of the urbanized and agricultural areas of the state. This collocation means that alluvial aquifers have been commonly used as a major water source over the last 70 years, possibly leading to declines in storage through time. We present preliminary estimates of historical groundwater storage changes in the alluvial aquifers of New Mexico, separated by USGS HUC-8 (hydrologic unit code, level 8) boundaries. These aquifers are mostly in Rio Grande and Basin-and-Range physiographic provinces-they are either in basins with the Rio Grande flowing through them or they are in the closed basins to the east and west of the Rio Grande basins. Our estimates are based on depth-to-water measurements available from the USGS online database, and datasets that conform to USGS measurement standards. Water level measurements affected by pumping or those that were taken during irrigation season were removed, except for locations in rangeland areas with poor data coverage. The measured depths-to-water are then used to determine a correlation length of water levels for each basin for every decade from the 1950s to present. The water levels are then interpolated using both ordinary kriging and inverse-distance-weighting methods. The interpolated fields are restricted to the radius of correlation lengths, and to Quaternary sediments mapped at the 1:500,000 scale.While our results are preliminary, we see a few patterns beginning to emerge. Groundwater withdrawals in closed basins appear to vary by the proportions of the water balance-pumping rates and locations compared with recharge rates and locations. In open basins, such as the El Paso-Las Cruces HUC or the Albuquerque HUC, the storage changes appear to be linked to the degree of connection of groundwater with the surface water, pumping demands and the presence of mountain-block recharge. Open basins are less sensitive than closed basins to pumping demands as long as (a) there is an initial connection with surface water, and (b) pumping does not lower the water to the point that the groundwater does not respond strongly to annual river flows. The Albuquerque HUC is a case where both of these conditions are met. The Santa Fe HUC and El Paso-Las Cruces HUCs, respectively, are examples of behaviors when (a) and (b) are not met, and groundwater is currently lowering due to greater demand independent of the river. Our results provide a coarse resolution view of groundwater storage in New Mexican alluvial aquifers. They do provide direct examples of how geology, hydrology and society are reflected in our groundwater resources at the basin scale.
This study differentiates four hydrostratigraphic units (HSUs) in the northwestern Albuquerque basin: the Upper, Middle, and Lower Rio Rancho HSUs underlain by the Zia HSU. This area hosts Rio Rancho (population of 104,000), which relies solely on groundwater for its municipal needs. We mapped these HSUs in the subsurface and assessed spatial trends in permeability and TDS. The study entailed constructing a 3D, geologic model showing the elevations of the bounding surfaces of these HSUs, and this model explicitly includes major faults. The HSUs exhibit layer-cake geometry, thicken towards the southeast, and thin over the Ziana horst in the northern part of Rio Rancho. Hydraulic conductivity data compiled from pumping tests indicate that the Upper Rio Rancho (RR) HSU has higher values compared to the Middle RR HSU: 1.1-6.4 ft/day, median of 2.9, vs. 3.2-21 ft/day, median of 9.3 (xx-xx = 10-90 percentile range). However, the thick, saturated portions of the Upper RR HSU are only found east of the Tamaya fault and in the southeastern part of the study area. The saturated Middle RR HSU is over 1,000 ft thick across most of the study area, including a north-trending prong between the Ziana horst and the Zia fault. Several wells indicate a coarsening upward trend in the Middle RR HSU, so areas where its upper part is saturated are more favorable than where just its lower part is saturated. There are no strong lateral permeability trends across the Middle RR HSU over most of the study area, but hydraulic conductivities from two pumping tests suggest higher permeability values in the southwest part of the study area, within 8 km northwest of the western end of Paseo del Norte. A northward increase in sand proportions also occurs north of the approximate latitude of well RRU-9 (35°20'0"), suggesting an increase in permeability that remains to be confirmed by pumping-test data. TDS values are 205-412 ppm in the Upper RR HSU, (excluding one well at 1,100 ppm) and 190-530 ppm in the Middle RR HSU, with the highest values in the latter occurring over the Ziana horst. The Lower RR HSU is mainly penetrated by wells on the Ziana horst, where it exhibits relatively high TDS values (478-1,400 ppm); the EPA recommends treatment for TDS >500 ppm. Various well-based permeability proxies and a single pumping test, in agreement with field observations, indicates it has relatively high permeability. The Lower RR HSU extends across the northern 2/3 of the study area, but may become finer-grained (corresponding to lower permeability) south of Southern Boulevard. The lower-middle Zia HSU is notably sandy, based on outcrop observations and wildcat oil well data. Its relatively higher elevation on the Ziana horst may possibly provide an accessible deep-water aquifer, but economical methods for water blending or desalinization would need to be formulated. The 3D geologic model along with maps of the potentiometric surface and TDS will be useful for managing groundwater resources in Rio Rancho and for potential groundwater-flow models of the a...
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