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Proposed Core Data Infrastructure

The overall Great Salt Lake Basin will be represented by selected focus areas in the contributing watersheds that are complemented by discrete measurements across the entire basin. For example, stream gages on the major rivers provide integration of surface water flux over their contributing watersheds. Networks for meteorological and snow pack monitoring, as well as groundwater monitoring also presently exist within the basin (see the existing data infrastructure page) providing a rich infrastructure context within which the observatory will be developed. Smaller areas will be observed with greater detail and focus. Selecting both the scale and location of these focus regions is a critical step in the observatory design.

Characteristic of the eastern Great Salt Lake Basins is steep topography that leads to large climatic gradients, yielding hydrologic systems that are dominated by non-linear interactions between snow deposition and snow melt in the mountains, stream flow and groundwater recharge in the mid-elevations, and evaporative losses from the desert floor at lower elevations. The essential hydrologic processes occurring in the Great Salt Lake Basins occur within the topographic, climatic, biological, and land-use gradients between the mountain catchments and basin bottoms. Hence, examination of hydrologic processes within mountain-to-basin transects is imperative in western hydrologic observatories.

The figure below illustrates in a simple manner our conceptualization of several key hydrologic processes in the Great Salt Lake Basin that will serve as a basis for delineating the basin into stores for the quantification of storages, flow paths and fluxes. Stores include the atmosphere, snow pack, streams, lakes and reservoirs, soil moisture, and groundwater. Core data will focus on observing these quantities at multiple nested scales. The base figure presented is a satellite image draped on a digital elevation model in order to highlight the short distances over which large ranges in elevation, climate, vegetation, and land use occurs. The compact nature of these mountain basin systems allows the development of densely instrumented areas to observe strong contrasts and process gradients.

Atmospheric fluxes will be quantified using an array of moisture and wind profilers that will be assimilated into mesoscale meteorological models. Remote sensing measurements will be used to observe energy balances, snow and evaporation, soil moisture and vegetation. Precipitation will be measured using radar, as well as shielded precipitation gages and snow pillows (SNOTEL). Meteorological flux stations (temperature, wind, humidity, eddy covariance) will monitor land to atmosphere exchange. In-situ soil moisture will be sampled using TDR and dielectric probes. Deep (greater than 300 m) multilevel sampling wells will be used to measure ground water levels, fluxes, and for sampling of age dating and environmental tracers. The deep wells will provide an unprecedented evaluation of flow and transport processes (including the interaction between groundwater and the thermal field) through a combined fractured rock and granular aquifer system. Stream gauging stations will include measurements of discharge, as well as water quality and tracers of interest.

Below are example components of core data infrastructure. This sampling of proposed infrastructure is provided in order to elicit input from the national hydrologic community regarding interest in proposing, taking part in, or even leading a particular component of the observatory. It is our belief that the optimal hydrologic observatory will have sufficient strength in local expertise to ensure success, but that domination by local investigators should be avoided. We are committed to expanding the observatory design team to achieve a balance that will ensure a full partnership among the local and national hydrologic research communities.

Mountain to basin transect

We propose at least one highly instrumented mountain-to-basin transect to investigate hydrologic processes extending from the mountain ridge top to the Great Salt Lake. The transect will range in elevation from about 1200 m to 3200 m, with a corresponding range in precipitation from about 15 cm/yr (West Desert) to 150 cm/yr (Wasatch Crest), range in evapotranspiration regimes from semi-arid to alpine, range in groundwater residence times from 10 to 10,000 years, and ranges in biome type from semi-arid shrubland to alpine forest, all within a 30 km distance depending on location.

One possible location of a transect is an east-west swath directed across the length of the Wasatch Front between North Ogden and Bountiful, where the axis of the Wasatch Mountains runs parallel and most promixal to the Great Salt Lake shoreline. This location is shown both in the concept-location diagram above, and forms the center of the red rectangle in the watershed map left. This particular location allows dense hydrologic monitoring within a 30 km distance while spanning a large spectrum of elevation, climate, vegetation, and land uses, all within 30 km of cities and universities that can provide necessary infrastructure support.

This transect location has access, instrument and communication advantages with respect to sampling, including direct line-of-sight to the Promontory Point WSR-88D radar and existing meteorological equipment and communication infrastructure at the Francis Peak FAA radar installation located at the ridge crest. Atmospheric measurements in the mountain-tobasin transect will extend meteorologically upwind of the Great Salt Lake (West Desert Basin) to allow observation of changes in air mass characteristics across the lake and mountain front. Between the Great Salt Lake and the portion of the Weber Basin directly east of the Wasatch ridge crest, atmospheric monitoring stations, spaced at 1-2 km will be coupled to snow pack monitoring stations and multilevel sampling wells. Less dense atmospheric, snowpack, and hydrologic infrastructure will be deployed within the eastern most portion of the Great Salt Lake Basin to the high Uinta Mountains. The overall transect dimension (including less dense monitoring west and east of the transect center) is shown by the red rectangle in the watershed map.

Click to enlarge

The transect will build upon recently obtained groundwater age data in the Salt Lake basin east of the Wasatch Mountains depicted in the figure right (Thiros and Manning, 2004). The change in age as a function of distance (age gradient) provides a direct measure of groundwater velocities and recharge rates (Manning, 2002). Noble gas thermometry has shown that the majority of groundwater in the basin is sourced in the mountain block. As such, the age data constitute a type of geochemical tomography in that they reflect (provide an "image" of) processes occurring in the adjacent (but not directly sampled) mountain block.

The transect will cross land use gradients in the Ogden-Weber canyons, and is situated in a location to capture long term changes in land use, water quality, water availability. The transect provides a compactness that presents not only logistical advantages, but also advantages in terms of increased interaction among researchers from different disciplines.

Lake sediment coring, tributary and lake sampling program

Lake sediment coring has been performed in the Great Salt Lake, Bear Lake, as well as smaller lakes within the Great Salt Lake Basin for broad ranging purposes including reconstruction of climate history (http://climchange.cr.usgs.gov/info/lacs) and examination of historical trends in trace-element, organic contaminant, and nutrient concentrations to determine anthropogenic sources of contaminants (Waddell and Giddings, 2004 http://water.usgs.gov/pubs/wri/wri034283/).

Vertical distribution of total polycyclic aromatic hydrocarbons (PAHs) in a gravity core from Farmington Bay, and relation to population growth in Salt Lake County, Utah. (USGS, 2004).

Lake sediment cores provide a record of long term climate and hydrologic processes, as well as long term water quality trends; since they avoid the issues associated with short record lengths, inconsistent analytical methods, and below-detection aqueous concentrations. Existing and ongoing core characterization work provides a basis for continued examination of these closed basin lakes as integrators and recorders of signals that might otherwise be difficult to discern based on discreet measurements made in individual tributary watersheds.

We propose to formalize a collaborative program involving core characterization activities, hydrologic monitoring activities, and biogeochemical investigations in order to relate climate, sediment accumulation, ecologic indicator, and contaminant records to corresponding processes in the contributing watersheds. Proposed infrastructure includes a program to core distal deltas of the three main tributaries and to monitor sediment and water quality parameters in contributing tributaries as well as the Great Salt Lake itself. Cores will allow comparison of prehistory to history, and contrasting of tributary watersheds in terms of pollen, other ecological markers, sediment flux, and contaminant flux.

Complementary monitoring of fluxes of dissolved and suspended constituents in tributaries to the Great Salt Lake and the lake itself is required in order relate their present flux to their historic accumulation within the lakes. These comparisons will also provide a basis for evaluation of biogeochemical processes controlling the fate of dissolved and suspended constituents within the watershed, and the consequences of these processes to ecological systems. Many specific issues can be examined within this context. For example, methyl Hg (biotoxic form of Hg) is quite elevated in the Great Salt Lake, especially in a deep brine layer that covers 50% of the south basin of the lake (David L. Naftz, USGS, personal communication). These elevated concentrations raise ecological concerns for the wetlands surrounding the GSL, which are of hemispheric significance to migratory waterfowl. Since Hg-methylation is mediated by sulfate reducing bacteria, it is likely that the rate of methyl-Hg production is controlled by lake level fluctuations via exposure and re-oxidation of sulfides. As another example, contaminant introduction to the Great Salt Lake may also result from ostensibly beneficial processes, for example, the Jordan Valley Water Conservancy District is presently considering treating impaired groundwater in the Salt Lake Valley, an action that could postpone importation of Bear River water and associated ecological consequences to that watershed. However, treatment of impaired water by reverse osmosis (RO) yields elevated Se and other heavy metals in the RO concentrate. The consequences of release of the RO concentrate to the wetlands surrounding the lake are as yet uncharacterized (see http://www.deq.utah.gov/issues/nrd/).

This proposed infrastructure will allow us to answer:

1. To what extent do lake sediment records of sediment transport and contaminant transport indicate differences in processes occurring within respective contributing watersheds over prehistoric versus historic predevelopment versus modern times? Can climatic and anthropogenic influences be clearly distinguished? Are differences apparent in the lake sediment record for watersheds of differing development histories?
2. Can the observed differences in lake sediment records be linked to known biogeochemical processes occurring in those watersheds? Are there critical locations at which these processes take place?
3. For known contaminant loadings to the contributing tributaries, are there contaminants for which there is no representation in the lake sediments despite expectations based on known processes? What are the processes that eliminate these contaminants from the system prior to deposition in the lake? Where in the hydrologic system are the eliminating processes located?

Riverbank filtration transects

The stress that increasing populations impart to the quality of surrounding water resources is demonstrated by the findings of Beer (1997), who found that along the Thames river in England, water passes at least six times through people before reaching the estuary. Scientists and policy makers share concern regarding the observed increases in levels of anthropogenic substances detected in aquatic environments. This is especially true for ubiquitous pesticides, pharmaceuticals, and personal care products (Verstraeten et al., 2002), which potentially disrupt the endocrine systems of aquatic organisms and potentially affect human health via drinking water and water recreation.

The 1993 outbreak of cryptosporidiosis in Milwaukee, Wisconsin infected 403,000 people and resulted in 70 fatalities (MacKenzie et al., 1994). This is one of many examples of the occasional failures of water treatment systems that occur even in industrialized nations. The problem is by no means strictly urban; as of the year 2000, half of U.S. drinking water wells tested had evidence of fecal contamination, and an estimated 750,000 to 5.9 million illnesses per year are estimated to result from contaminated groundwaters in the U.S. (Macler and Merkle, 2000). Although the issue of water supply contamination by pathogens is not restricted to urban settings, the issue is of great importance to cities, where the ability to increase water supply without appropriation of new sources will depend on the ability to treat impaired sources economically.

Riverbank filtration is an emerging water treatment technology that promises partial, or in some cases complete, treatment of impaired water (Ray et al., 2002). Riverbank filtration is fundamentally a hydrologic process, since it relies on naturally occurring contaminant removal mechanisms (e.g. adsorption of dissolved constituents, filtration and straining of suspended constituents) operating in natural riverbank materials during transport from a river to a receiving well. During riverbank filtration, it is crucial to ensure a sufficiently high rate of attachment (and low rate of detachment) of suspended constituents (e.g. protozoan, bacterial, or viral pathogens) during transport to water supply wells, as reviewed by Schijven et al. (2002).

Hydrologists are presently able to predict colloid/microbe attachment rates during transport in porous media under conditions where colloids/microbes experience attraction only to the porous media grain surfaces. However, in natural porous media, a repulsive component always exists in colloid-surface interactions, confounding our ability to predict the transport of colloids/microbes in groundwater aquifers and riverbank materials. The results obtained from both laboratory and field studies simply do not fit theory (Li et al., 2004; Li and Johnson, 2004; Tong et al., 2004). Theory predicts log-linear decreases in microbial concentrations with distance from source, whereas experiments show that such distributions mostly do not apply in environmental media. Furthermore, very little is known about the controls on colloid/microbe release from sediment grain surfaces back into groundwater, other than that it does occur at relatively slow rates that are potentially significant over long periods (weeks to years or more) (Zhang et al., 2001). Attachment and release of biological contaminants is also complicated by the potential influence of biological activity on transport (e.g. via motility, changes in surface properties with metabolic activity, cell division mediated transport, etc., as reviewed in (Murphy and Ginn, 2000). The situation is further and greatly complicated by the potential for water-rock interaction during transport, which affects not only the aqueous chemistry that governs physicochemical aspects of attachment and detachment, but also the redox and nutrient conditions that govern biological activity (Murphy and Ginn, 2000).

Because riverbank filtration wells are typically placed in relatively coarse sediments in order to maximize rate of groundwater recovery, the riverbed itself (typically a mixture of coarse and fine materials) is considered to be an important first line for removal of dissolved and suspended contaminants in the river water (Gollnitz, 2002). However, the thickness of riverbeds is temporally variable, especially during floods, hence understanding changes in the permeability and thickness of riverbeds as a function of flood stage is important to maintaining water quality during riverbank filtration. As well, contaminant loading into rivers increases during flood, compounding the difficulty in maintaining quality of riverbank filtered water.

It is proposed to place a transect of shallow multi-depth sampler wells from the Jordan River to the riverbank filtration gallery operated by the Jordan Valley Water Conservancy District in order to examine the distribution of river-derived contaminants within the sediments up-gradient of the recovery wells. This will allow determination of the locations of primary points of removal or degradation of dissolved and suspended contaminants, and to determine the effects of flood and scour on these distributions.

References

Beer A.J., 1997, Something in the Water, Biologist, 44(2), 296.

Gollnitz W.D., 2002, Infiltration Rate Variability and Needs, in Riverbank Filtration: Improving Source Water Quality, Ray C., Melin G., Linsky R.B.,eds. Kluwer Academic Publishers, Boston, U.S.A. and National Water Research Institute, Fountain Valley, U.S.A., 365 pp.

Li X., and W.P. Johnson, 2004, Non-Monotonic Variations in Removal Rate Coefficients of Microspheres in Porous Media under Unfavorable Deposition Conditions, in review in Environmental Science & Technology.

Li X., T.D. Scheibe, and W.P. Johnson, 2004, Apparent Decreases in Colloid Removal Rate Coefficients with Distance of Transport under Unfavorable Deposition Conditions: A General Phenomenon, in review in Environmental Science & Technology.

Macler B.A. and Merkle J.C., 2000, Current knowledge on groundwater microbial pathogens and their control, Hydrogeo. J., 8, 29-40.

Murphy, E.M., and Ginn T.R., 2000, Modeling microbial processes in porous media, Hydrogeology Journal, 8, 142-158.

Ray C., Schubert J., Linsky R.B., and Melin G., 2002, Introduction, in Riverbank Filtration: Improving Source Water Quality, Ray C., Melin G., Linsky R.B.,eds. Kluwer Academic Publishers, Boston, U.S.A. and National Water Research Institute, Fountain Valley, U.S.A., 365 pp.

Schijven J., Gerger P., and Miettinen L., 2002, Removal of Pathogens, Surrogates, Indicators, and Toxins Using Riverbank Filtration, in Riverbank Filtration: Improving Source Water Quality, Ray C., Melin G., Linsky R.B.,eds. Kluwer Academic Publishers, Boston, U.S.A. and National Water Research Institute, Fountain Valley, U.S.A., 365 pp.

Tong M., X. Li, C. Brow, and W.P. Johnson, 2004, Detachment-Influenced Transport of an Adhesion-Deficient Bacterial Strain in Water-Reactive Porous Media, in review in Environmental Science & Technology.

Verstaeten I.M., Heberer T., and Scheytt T, 2002, Occurence, Characteristics, Transport, and Fate of Pesticides, Pharmaceuticals, Industrial Products, and Personal Care Products at Riverbank Filtration Sites, in Riverbank Filtration: Improving Source Water Quality, Ray C., Melin G., Linsky R.B.,eds. Kluwer Academic Publishers, Boston, U.S.A. and National Water Research Institute, Fountain Valley, U.S.A., 365 pp.

Zhang, P., Johnson, W.P., Scheibe, T.D., Choi, K., and Dobbs, F.G., 2001, Extended Tailing of Bacterial Concentrations at the Narrow Channel Site, Oyster, VA, Water Resources Research, 37(11), 2687-2698.