Patent Application
20140009302
The present invention relates generally to the field of well water information and devices and methods of retrieving and recording said information. More particularly, the present invention relates to devices and methods of continuously monitoring water level in a well.
Many residential homeowners rely on the use of a well to supply water to their home. Likewise, many farmers rely on the use of a well to supply water to irrigate crops or to keep animals hydrated. Private water wells are a common feature in areas where municipal or city water services are unavailable or where surface supplies are not sufficient or accessible. Water wells are commonly used to source groundwater where naturally occurring groundwater exists in spaces between rocks and/or sand. The wells themselves are bore holes either drilled or pressed into or through the ground into which casing pipes, screens, pumps and other water plumbing are installed. Groundwater seeps through openings in the casing pipe called screens. Water can be pumped via these wells, either with an above ground vacuum pump or, where the water is deeper than 30 feet, with a submersed pump that creates upward pressure to move the water to the surface.
A conventional well typically includes a borehole from the surface to a required depth to reach the ground water. A casing pipe is inserted into the borehole and grout is used to seal the space between the casing pipe and the earth. A pump (either submersed or above the ground water surface, depending on depth) is attached to the water pipe for transportation of water from the well to the point of use. The well is capped at the well head on the ground surface with a well cap. Typically, information which may include a service contractor's phone number and a date of service may be recorded on the well cap.
Water well construction (and sometimes site selection or location advisement) is done by a well driller, who takes care to design the well to meet the needs of the people who will use the water. The well driller, in the process of planning and drilling, will determine where there is ample groundwater, and will size the length and diameter of the well and casing pipe and the capacity and location of the pump accordingly. The driller will take special care to know the top elevation and the productivity of the groundwater table. Elevation is often found by measuring down from the well head (top of the well) to the water surface. Productivity of the well is inferred by measuring the elevation of the water and time it takes to return to a resting level after a pumping event has removed water to the well, a process called recovery. Together with elevation and productivity, the final pump selection is made and construction can be completed.
This water information is necessary to determine the well location in relation to the location of a building, a field of crops, or a neighborhood. At also informs the semi-permanent placement of the pump in the well. If the pump is placed too high in the well, it risks running dry and breaking prematurely. If the pump is placed too low in the well, then the owner will pay extra for the energy required to pump water an unnecessary distance. This information is typically only gathered once, however, at the time of construction. The lack of subsequent information gathering sometimes leads to new issues with the well or the pump that could have been prevented if only the well driller or homeowner had such information.
A borehole well may be considered to be healthy as long as sufficient ground water seeps through a screen section of the casing pipe into the column to allow for water to be pumped from the well. This state of balanced supply and demand is called a “safe yield”. As is known to those skilled in the art, a borehole well, the water system, and sometimes the pump equipment will not tolerate long periods of an unsafe yield. For example, a submersible pump must be kept submerged under water for proper operation. Failure to keep the pump submerged causes the pump to overheat and fail. Failure of a pump requires the well to be opened by a technician and the pump must be physically retrieved and repaired or replaced. Thus, a previously recognized problem has been that it is difficult to know the water level in the well and how close the pump may be to reaching the unsafe yield point. In a worst-case example, a borehole well will be pumped dry, the pump will fail, and the water table will have been permanently lowered in the area, effectively rendering the well useless. Needless to say, it is desirable to know about water levels in the casing pipe.
Existing methods of determining water table levels include mounting a sensor under the water in the well with wires communicating to the well head, pressure sensors built into the pump, and opening the well head to physically inspect the well with a plumb bob. Various other methods are known which all necessitate physically opening the well head to inspect the water table level.
One unsatisfactory previously recognized approach, in an attempt to solve the problem referred to herein, involves use of an airline to compress air in the casing pipe in an attempt to raise water to the surface, indicating the level. Another unsatisfactory method is to use a simple sonar instrument, not unlike a consumer grade fish finder, to find water level in the well. Certain environmental factors, like temperature, casing pipe material, well straightness, depth, and obstructions can render these devices inaccurate, so they are not as popular as mechanical tapes. In yet another previously recognized approach, contractors often carry a well level device that includes a moisture sensor at the end of a measuring tape that is temporarily inserted into a well and which makes a sound when it touches water, indicating the distance to the water. This technique is known to be reliable and inexpensive, but like the other previously described techniques, it is only designed for the well contractor's use to take one reading at a time, and to not log data or spot trends without repeat visits and manual collection, which is impractical and rarely happens.
A disadvantage of these previously recognized approaches is that due to water levels in the ground being dynamic, the data acquired is quickly dated and inaccurate once the technician completes the test. There is virtually no ongoing monitoring of safe yields of the well's water level. Additionally, users do not know if they are using more water than they should until it is too late. One common indication of overuse is that the pump fails due to dry run, indicated by a lack of running water from faucets or to toilets or appliances. Failures caused by overuse can be very expensive to repair, ranging in price from thousands of dollars to replace a pump or clear a well, to tens of thousands of dollars to dig a deeper well. In some cases, systemic overuse by many consumers in a region can even tax the ground water to the point of concentrating pollution or even running everyone's well dry. Homes in areas where there is severe water risk can quickly lose value.
On higher capacity, higher criticality water wells owned by water municipalities and some high-use agriculture businesses, water elevation information is collected continuously with pressure sensors mounted in the well under the water level connected to data logging equipment at the surface. Data provided by these devices is vital for controlling flow and therefore system performance. So a pressure sensor is part of a larger SCADA (Supervisory Control and Data Acquisition) system that keeps water flowing continuously. But these devices are expensive to install and maintain and may be part of a larger control network and scheme so they are not suitable or economically viable for homeowner or intermittent farm or business use.
When commissioning or repairing a well, a well driller may also perform a “pump test” to determine the ideal location for the pump. Using a sacrificial test pump, the well driller tests the pumping level and drawdown of the well, that is, the changed water elevation while the pump is running at its target capacity. The process involves installing the sacrificial test pump in the well deep under the static water level and running it at a flow rate equal to the anticipated peak demand of the well. When water is pumped to the surface, the water level in the well drops dramatically at first, and then the rate of decline begins to decrease until the pressure created by the water table equals the pressure created by the pump and groundwater runs into the well at the same rate that the well pumps water to the surface. The level of the water at which the pressure created by the water table equals the pressure created by the pump is the ideal vertical position of a pump in the column. Of course, the ideal vertical position of the pump at the time of commission or repairing may not be the ideal vertical position in a day, a month, or even years after the pump test is performed. However, because performing pump tests as described are costly and time intensive, they are not performed until repair is needed.
Finally, whereas in the recent past, sparse rural population, stable weather and slower agricultural and economic development did not threaten the natural recharge capabilities of most groundwater sources, today, population, overconsumption and climate changes have begun to tax the groundwater resource measurably. Hydro-geologists call this “unsafe yield.” So water wells constructed a few years ago based on a groundwater elevation measured at the time are not able to produce as designed, and often fail prematurely.
As discussed, monitoring groundwater elevation continuously in residential and agricultural wells is becoming more important, but existing monitoring solutions are not effective. Measuring with a tape continuously is impractical and will always only be for one time use (a snapshot taken at one moment). Measuring with inaccurate sensors does not yield usable information. Outfitting intermittent use wells with pressure sensors and control networks is not cost effective or even necessary. Smart operations methods and an understanding of trends are needed as conditions change.
What is needed therefore is a device that allows monitoring of the well's water level on a continual basis. What is also needed is a way to monitor the well's water level preferably without repeated removal of the well head. Further, what is needed is a way to retrofit existing wells with a device that continuously monitors the well's water level preferably without repeated removal of the well head. Heretofore, these requirements have not been fully met without incurring various disadvantages.
The present invention relates to a well head water level sensing system that allows continuous monitoring of water level in a residential well. The well head water level sensing system includes a signal generator, a triggering circuit, a tunable listening device, environmental (e.g., temperature and/or humidity) sensors for calibration, a clock, a secondary listening sensor for timed or provoked events, a data logger, and power and communication circuits. The well head water level sensing system relies on the sonar effect and the inherent resonant frequency of a tube to estimate the distance from the signal generator to the water level in the well.
An alternative embodiment of the invention is a water level sensing device having a simple, solar-powered sensor and communication module that gathers information about the level of water in a borehole-style water well and sends the information to a database that a homeowner can access via a computer, handheld device, or smart phone. The water level sensor tracks the level of water in the well, how it changes over time, the pace of recharge (water replenishment from the groundwater source), and can be programmed to send alerts to interested parties when user-predetermined thresholds are reached. The water level sensor and a website enable a well owner to use water mindfully within safe yield, and can help prevent costly water or well shortages, equipment failures, or other emergencies.
The water level sensor can preferably be attached to the exposed well head by a handy homeowner using a few common tools. In some applications, only a replaceable battery is required to power the sensor. And in others, power can be harvested from existing power wiring, without connections, using a current transducer and a power monitoring circuit. And in others, a photovoltaic cell affixed to the sensor or, optionally, on a flexible wand to raise the solar cell, charges and recharges a battery which powers all functions. A sensor is installed just inside the existing well cap, through vent holes that may be in the existing well cap, or within a new, replacement well. The data it collects is compiled in memory and sent to a database, where it is stored and analyzed.
It will be understood by those skilled in the art that one or more aspects of this invention can meet certain objectives, while one or more other aspects can lead to certain other objectives. Other objects, features, benefits and advantages of the present invention will be apparent in this summary and descriptions of the disclosed embodiment, and will be readily apparent to those skilled in the art. Such objects, features, benefits and advantages will be apparent from the above as taken in conjunction with the accompanying figures and all reasonable inferences to be drawn therefrom.
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A well head water level sensor for a well and its related components may alternatively be placed on the outside of the casing pipe 40 or on top of the well cap 45.
In this configuration, sensors may be attached to the existing well hardware and is configured to be able to gather information through that hardware.
As shown in the flowchart of
The well head water level sensor 100, 200, 300 relies on two physical phenomena to gather information: 1.) the sonar effect to estimate distances to surfaces, and 2.) the inherent resonant frequency of a tube to help distinguish between obstructions, friction, bends and curves, and the actual water surface. This phenomenon can be observed in any wind instrument or pipe organ: a tube of a given length will resonate at a given frequency. By combining these two functions in the well head water level sensor 100, 200, 300, it can be made from common, albeit modern, and therefore capable and small components, and be placed at the top of the well, rather than in the water, and be highly accurate across a wide range of well sizes, shapes and configurations.
In the embodiments shown, the signal generator 102 generates a digitized low amplitude single pulse sine-wave sound (frequency is not a major factor in operation, but is determined by the limits of the signal generator, amplitude is determined by balancing well size and power consumption) and then listening. Many echo responses are heard, some larger and longer than others. Since wells differ, it is common for an echo created by an obstruction to be misinterpreted as water elevation, when it is not. For that reason, practitioners distrust basic sonar tools at worst, or consider them to be useful only for a low-resolution estimate. To improve the accuracy of the reading, the well head water level sensor 100, 200, 300 proceeds to a second step: reflections are analyzed for time, and the signal generator 102 responds by sending a new batch of single pulses, this time, coordinated at period identified by the largest reflection, which is assumed to be the natural resonant frequency of the distance of the tube from generator to the most complete obstruction, which in this case is the water surface.
If the timing is, in fact, the resonant frequency of the pipe distance to the water surface, the heard responses will begin to gain in amplitude. This occurs because the source pulse and the return echo are in perfect phase and reinforces the sound pressure level at the receiver. If this gain in amplitude phenomena is not observed, the signal generator 102 will alter its pulse timing to the next largest response, and so on. Once resonance is identified, it is confirmed by tuning the timing of additional pulses. As a confirmation to prevent a false positive occurring from some geometric feature of the well (or miscellaneous partial obstructions within the well), the source pulse timing is shifted to lag or lead 180 degrees in time relative to the source sound wave frequency. If the prior assumed resonance pulse timing that caused a gain in amplitude is the actual echo from the water's surface, the amplitude of pulses at the receiver will decrease significantly due to the source pulse and the echo canceling each other and thereby reducing the sound pressure at the receiver. The lowest pulse timing that causes these to conditions to occur, can only be the true resonant frequency of the well.
Because the well head water level sensor 100, 200, 300 performs a series of tests to find both sound reflections and the well's resonant frequency, the sensor can be accurate in and adapt to nearly any drilled well environment.
The well head water level sensor 100, 200, 300 also includes an environmental sensor 108 because the speed of sound in the air is affected by the air temperature and relative humidity. The environmental sensor 108 includes a temperature reading device 110, positioned at a location accounting for variations in surface and deep depth temperatures, and providing information to adjust final water depth calculations.
As a final check of data integrity after initial power up, readings are compared before and after a pumping event signaled by the triggering circuit 104. If no change in time response data is observed, the device will assume that it is not seeing the variable water surface, but a permanent obstruction, and will recalibrate to the next most likely response signal. Simple math is then used to calculate water elevation from sensed data, calibrated with readings from the environmental sensor 108, and a log of time-stamped readings is assembled and made ready to be shared.
To enable semi-continuous monitoring of a water well, it is necessary to position the sensors 102, 108 in such a way that they can see into the well while not needing to open the well or expose the water to open air or contamination and to leave them there, to operate over months and years. Additionally, its work must be done and information collected and accessed or transmitted at the surface without special tools or connections. The embodiments shown in
A transmission device within well head water level sensor 6 transmits the computed ground water level to a wireless network which may be a cellular network, a satellite network, or any other suitable wireless network. The wireless network may then relay the computed ground water level to a globally accessible network 70 which may include the Internet, the World Wide Web, or any other known globally accessible network. A handheld device which may include a smart phone, a tablet computer, a pager, or any computer that has access to the globally-accessible network 70 may then download 80 the ground water level information from the water well and display the ground water level information in any form, including a graph. Well head water level sensor 6 may be programmed to periodically transmit a data set which may include the ground water level to the wireless network.
Well head water level sensor 6 is shown with a whip module 14 that includes a shaft 20, a solar panel 25, and a base plate 15. As shown, a light emitting diode 35 indicates whether well head water level sensor 6 is functioning properly. The light emitting diode 35 may also be programmed to flash or change color to indicate warnings or to indicate any programmable message.
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The well head water level sensor 100, 200, 300, 6, 7 is designed to be installed and forgotten. The photovoltaic cell is large enough to provide power for full operation during the day. The battery provides enough power for night time operation, and for extended periods of cloud cover. In the embodiments shown, the battery life is approximately 5 years, when used in a well with a depth of approximately 100 feet and approximating other power consumption variables. Of course, other batteries or power supplies may be used to accommodate wells of different depths or any other reason without departing from the invention. The housing is waterproof, tamper-proof, vermin-proof, and durable enough to withstand small contact with branches, weeds, or a passing lawn mower. An optional solar wand may also be used to extend the height of the solar photovoltaic cells, accounting for deep snow, or bush and plant growth.
Although the invention has been herein described in what is perceived to be the most practical and preferred embodiments, it is to be understood that the invention is not intended to be limited to the specific embodiments set forth above. Rather, it is recognized that modifications may be made by one of skill in the art of the invention without departing from the spirit or intent of the invention and, therefore, the invention is to be taken as including all reasonable equivalents to the subject matter of the appended claims and the description of the invention herein.
This application is based on and claims priority to U.S. Provisional Patent Application No. 61/665,976 filed on Jun. 29, 2012, which is incorporated herein by reference in its entirety for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| 61665976 | Jun 2012 | US |
