Finding enough water to sustain a well can sometimes be challenging. Local well drillers and logs are an invaluable resource. Occasionally, newly drilled wells underperform at the client's expense. OWLS offers cost-effective groundwater locating services using Seismoelectrics technology to help find well water and minimize risk in advance of drilling.
A newly drilled well is much more than a hole in the ground. Rates vary, but average drilling costs run $30-$60 per foot, making it a considerable investment regardless of the well's intended purpose. In most areas, water wells are being drilled deeper, which adds to the overall cost, in terms of drilling and energy required to bring the water to the surface. Finding water before drilling minimizes overall risk and costs associated with drilling a new well or deepening an existing well. Oil and mining companies invest in, refine, and use geophysics extensively to locate resources. The same methodologies are used for finding groundwater. Seismoelectrics, discovered in the oil industry and refined for groundwater locating services, offers a portable, rapidly deployed, economic and minimally invasive solution. It detects the presence of groundwater, depth to the water table, aquifer thickness and potential yield by calibration from a local well in similar geology. A survey of six soundings will typically cover an acre of land and can be done in a day by one operator. Geology determines structure and permeability (flow rates). In fractured rock aquifers, for example, more soundings are often needed to identify interconnected permeable zones. The amount of water required from a well determines survey size and cost, e.g., a homeowner versus a municipal, or agricultural well. Geology, topography, site access and presence of man-made cultural noise sources also factor into survey design and cost.
In simple terms, a pressure or seismic wave generated from a surface source compress underlying rock and sediment layers at different speeds relative to the rock type. When the radiating pressure wave encounters permeable fluids, i.e., groundwater, an electrical charge is generated, which is recorded at the surface by an antenna array centered over the seismic shot point. The electrical responses recorded are typically measured in milli- to microvolts. In short, the more permeable or interconnected the groundwater in the underlying geology, the higher the voltages recorded, the more GPM. The results are computer modeled using the system's software algorithms to determine depth to water, aquifer thickness, and with proper calibration from nearby wells, potential well yield (hydraulic conductivity in liters per second (l/s) or gallons per minute (GPM)). OWLS uses a patented system, the GF6, manufactured in the U.S., with a proven track record of 20 years in groundwater locating services and worldwide sales.
A well planned and efficient groundwater survey includes a review of local geology and groundwater trends from nearby well logs, geological maps and other available resources depending on the region. Underlying geology determines permeability and can sometimes vary by orders of magnitude over relatively short distances. A seismoelectrics groundwater survey can provide valuable insights about potential water, or lack thereof, that can be used to decide whether to go forward with a project, for a fraction of the cost of drilling. OWLS personnel have completed post-baccalaureate coursework in hydrogeology, and work with registered Hydrogeologists, Geologists or Geophysicists in compliance with state regulations.
A typical groundwater survey consists of several soundings collected along a traverse or grid over a test area of interest. For domestic use, a minimum of 6 soundings are collected approximately 20 meters (66 feet) or less apart in proximity to the desired well site, or based on site conditions. For agricultural wells, a minimum of 12 soundings are required at the same spacing. More soundings increase accuracy of the results. In fractured rock aquifers, more soundings increase the likelihood of locating a zone of high permeability relative to surrounding geology. Proper planning is key to a successful survey design.
I started OWLS to offer cost-effective groundwater locating services for clients looking to find water before drilling a well prior to the expense and effort of drilling. I have 22 years field experience supervising electrical and electromagnetic geophysics data acquisition projects in mining, groundwater, geothermal and Unexploded Ordnance (UXO) detection, and 8 years in groundwater surveying using seismoelectrics to verify well targets in conjunction with electromagnetics geophysics on municipal well development projects. The latter includes well drilling oversight, construction, and development. Additionally, I have spent time on mud-rotary and dual-rotary rigs logging geological and water chemistry samples. I have performed sieve analysis for well screen selection and have designed and conducted aquifer pumping tests and analyses.
Customers have questions, we have answers. Display the most frequently asked questions, so everybody benefits.
Q: What about dowsing, witching, or divining?
A: There is much written about water dowsing. It's been around for centuries. The technique is not regulated as it falls under religious belief.
https://www.usgs.gov/special-topic/water-science-school/science/water-dowsing
OWLS doesn't endorse or denounce it. However, as wells run dry in many places, your hard-earned money might be better spent on performing a scientifically based groundwater survey. Also, consider that a high percentage of wells drilled only penetrate the top of the water table. As more groundwater is pumped, and not replenished due to drought conditions, many wells are running dry. As a result, wells are currently being drilled deeper.
Q: What about other geophysics techniques?
A: There are many commercially available geophysics techniques used for finding groundwater. Seismoelectrics is unique in that it detects permeable groundwater directly. If there is no permeability, there is no corresponding seismoelectrics signal. If the water is saline, there is no corresponding signal. In contrast, geophysical techniques, e.g., electrical resistivity, derive the resistivity of the rocks and soils being measured directly from the water content in the pore spaces, the resistivity (salinity) of the water, and arrangement of the pores, i.e., porosity, and indirectly, permeability. Electrical and electromagnetic resistivity surveys provide keys to geologic structure and water table trends; however, permeability can sometimes be the inverse of porosity, e.g., clayey soils with high water content (porosity), but low permeability. Obsidian Groundwater Locating Services has used both electromagnetics and seismoelectrics concurrently on groundwater surveying projects to find water before drilling. There is no foolproof method, and each technique has differently designed outputs and limitations, including seismoelectrics.
Q: What are some key limitations to seismoelectrics?
A: 1) Seismoelectrics is a sounding technique, so each sounding is a specific point as opposed to a resistivity survey, for example, where a survey line is designed, and the data acquired is processed to provide a larger picture of the area by combining all data collected, usually in the form of a priori inversion and modeling programs. 2) The electrical signals generated from the seismic wave are quite small, so cultural noise is an ever-present factor. 3) Data quality can sometimes be difficult to achieve, particularly in less-than-ideal conditions, e.g., rocky soils. OWLS has the training and background to mitigate these limitations.
Quick read and good summary of seismoelectrics methodology by a successful groundwater surveyor in Canada.
A good article in The Driller about utilizing seismolectrics technology to find water before drilling.
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