Groundwater flow rates estimation

In the simplest case, groundwater-flow rates for lakes at isotopic steady state (or those with relatively long hydraulic-residence times) can be estimated from data on average annual precipitation rates average annual evaporation rates the isotopic compositions of precipitation, lake water, and inflowing ground-water and relative humidity and lake temperature. 

The isotope mass-balance method is not as useful for estimating groundwater-flow rates for groundwater-poor lakes as it is for lakes that receive substantial quantities of groundwater. Solute tracers, such as dissolved calcium, may be useful in assessing... 

Volume flow rates of incoming hydrothermal solution and groundwater to each reservoir were estimated from the temperature of reservoirs and initial hydrothermal solution (250°C) and groundwater (25°C)... 

In electrochemical treatment of extracted groundwater, the operating costs for electrode consumption, power, and acid for the electrochemical unit are estimated at approximately 10 cents per 1000 gal of groundwater treated. At an anticipated flow rate of 20 gal/min (gpm), the operating costs are approximately 1000 annually. Labor and waste disposal costs for the electrochemical treatment process are estimated to be approximately 50 per day (D168869, p. 7-14). 

The evaluation sited a number of factors that could affect process costs for groundwater treatment, including flow rate, type and concentration of contaminants, groundwater chemistry, physical site conditions, site location, availability of utilities, and treatment goals. Assumptions made for the cost estimate include any suspended solids are removed prior to CPFM treatment, the influent has an optimum pH of 8 to 9, and the ambient temperature of the influent is between 20 and 35°C. It was assumed that the system would be operational on an automated, continuous-flow mode, 7 days per week, 24 hours per day. This would lead to approximately 52.4 million gallons of water being treated in a 1-year period (D10957J, p. 22). 

In 1991, the U.S. Environmental Protection Agency (EPA) Superfund Innovative Technology Evaluation (SITE) demonstration program evaluated the AquaDetox/SVE system. The demonstration took place at the San Fernando Valley Groundwater Basin Superfund site in Burbank, California. Based on this demonstration, cost estimates for a full-scale deployment of the system were prepared. Three treatment flow rates were evaluated, based on the 1200-gallon-per-minute (gpm) system used at the Lockheed site 500, 1000, and 3000 gpm. Capital costs and annual operational and maintenance (O M) costs were estimated in 1991 dollars and are shown in Table 1. 

Physical Approaches. Groundwater-exchange rates with lakes are traditionally estimated by careful measurements of hydraulic potentials within the groundwater system, followed by application of Darcy s law in the form of flow-net analysis or numerical modeling. However, these measurements can be time-consuming and costly, and can require monthly to weekly measurements at many piezometers to examine the three-dimensional nature of the hydraulic-potential field. In addition, characterization of the hydraulic conductivity of the aquifer is critical to physical approaches and typically leads to results with large uncertainties (I, 2). 

By use of eq 11, this isotopic information, and the average annual precipitation and evaporation rates (0.79 and 0.52 m/year, respectively), the average annual groundwater inflow rate to Sparkling Lake was estimated to be 0.27 m/year (expressed as the volumetric flow rate divided by the surface... 

The rate at which groundwater moves through an aquifer is not usually directly measurable, and thus it must be estimated from known relationships among measurable parameters. The discussion of groundwater flow presented here is only an introduction to the topic many of the relationships described are approximations, and most are restricted in their applicability to situations in which the flow of groundwater is steady over time. When a more detailed analysis is necessary, the reader is referred to the following texts on ground-water Bear (1972, 1979), Freeze and Cherry (1979), Heath (1984), Strack (1989), McWhorter and Sunada (1977), and Davis and de Wiest (1966). 

Infrared thermography Infrared imaging has been used to identify the location and spatial variability of SGD by exploiting the temperature difference between surface water and groundwater at certain times of the year. While this technique is quite useful for identifying spatial discharge patterns, it has not yet been applied to estimating flow rates. 

So we can consider that the borehole flow rates from the gas monitoring (0.11/h) are not representative. We can estimate that if groundwater levels rise we may obtain higher rates in the short term (say, for up to 8 h). So we will estimate that 21/h borehole flow rate is more representative of the site. 

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