Ventilation of underground porosity storage reservoirs

Abstract

An underground porosity reservoir includes substantially impermeable barriers and an aquiclude surrounding a volume of alluvial deposits for storing water within the pore spaces of the alluvial deposits. A conduit positioned below a surface layer of the reservoir includes an interior volume that communicates with the pore spaces of the alluvial deposits. An air vent connects the interior volume of the conduit with atmospheric air above the reservoir and allows air to pass to and from the pore spaces of the reservoir. Ventilation of the porosity reservoir provides pressure-relief during reservoir filling operations (when the incoming water would otherwise cause an increase in air pressure within the reservoir), and further provides a vacuum-break as water is extracted from the reservoir (i.e., air from the conduit enters the pore spaces as the water is extracted).

Description

RELATED APPLICATIONS[0001]This application claims priority from U.S. Provisional Application No. 60 / 847,143, filed Sep. 26, 2006, which is hereby incorporated herein by reference.FIELD OF THE INVENTION[0002]This application relates generally to a method of ventilating an underground porosity reservoir, and more particularly to a method of providing pressure-relief as the reservoir is filled with water and a vacuum-break as water is extracted from the reservoir.BACKGROUND OF THE INVENTION[0003]It is becoming increasingly difficult, both in terms of cost and site availability, to construct conventional open reservoirs for the storage of water. Such reservoirs typically require the construction of a dam across a river, thereby flooding vast expanses of land upstream of the dam while severely curtailing the flow of water downstream from the dam. In light of the increasing value of water and the complexities of the various water laws across different jurisdictions, it is becoming prohibi...

AI Technical Summary

Benefits of technology

[0012]The present invention includes an underground porosity reservoir for storing water in alluvial deposits, wherein the reservoir is formed by one or more substantially water-impermeable barriers and an aquiclude that surround a volume of alluvial materials, so that water can be stored within the spaces or pores between the alluvial materials. A conduit is positioned below a surface layer of the reservoir so that an interior volume of the conduit communicates with the alluvial deposits of the reservoir (e.g., through an opening at the end of the conduit or through a series of perforations formed along the conduit). Additionally, an air vent is provided for connecting the interior volume of the conduit with air at substantially atmospheric pressure above the reservoir. Establishing communication between the underground conduit and the atmosphere above the reservoir allows air to pass to and from the reservoir during extraction and recharge operations, respectively. In particular, the atmospheric air within the interior volume of the conduit communicates with the pore spaces of the alluvial deposits within the reservoir to provide a path for (1) air entrapped within the pore spaces of the alluvial deposits to escape the reservoir as the reservoir is filled with water, and / or (2) air to enter the reservoir in order to substantially eliminate a partial vacuum formed within the pore spaces of the alluvial deposits as water is pumped from the reservoir.

[0013]In one preferred embodiment, an extraction and / or recharge well is used for pumping water out of (and into) the reservoir, and the conduit is positioned to run adjacent to the well. In a further embodiment, each conduit comprises a perforated pipe positioned just below the interface of the surface material (e.g., topsoil) and the alluvial deposits within the reservoir, and the perforated pipe is surrounded by coarse bedding material in order to maximize the transfer of air into and out of the conduit.

[0014]Another aspect of the present invention provides a method ventilating an underground porosity reservoir, wherein the reservoir is formed by one or more substantially water-impermeable barriers and an aquiclude, and water is stored within pore spaces of the alluvial material contained within the reservoir. The method includes the initial step of positioning a conduit below a surface layer of the reservoir so that an interior volume of the conduit communicates with the pore spaces of the reservoir. Next, air at substantially atmospheric pressure is provided to the interior volume of the conduit, such as by extending an air vent between the conduit and a region above the surface of the reservoir. In one embodiment, the method includes filling the reservoir with water so that air entrapped within the pore spaces of the alluvial material is forced upward and out of the reservoir through the conduit and the air vent. In a further embodiment, water is extracted from the reservoir so that a partial vacuum is formed within the pore spaces of the alluvial material as water is removed from the reservoir. Air within the conduit is then drawn into the reservoir to substantially eliminate the partial vacuum formed in the pore spaces of the alluvial material.

Problems solved by technology

It is becoming increasingly difficult, both in terms of cost and site availability, to construct conventional open reservoirs for the storage of water.

Such reservoirs typically require the construction of a dam across a river, thereby flooding vast expanses of land upstream of the dam while severely curtailing the flow of water downstream from the dam.

In light of the increasing value of water and the complexities of the various water laws across different jurisdictions, it is becoming prohibitively difficult to form an open reservoir in this manner.

A further disadvantage of open reservoirs is the high degree of evaporative losses experienced by such reservoirs due to the relatively large air / water interface.

Specifically, in arid climates (such as those found in the Western United States), open reservoirs are subject to extremely large evaporative losses.

Indeed, such evaporative losses are typically greatest where water is needed most.

Should excessive air pressure be allowed to build up in the alluvial materials during the recharge and extraction of water from porosity reservoirs, a cracking in the surface or separation of the native top soil from the alluvial material may occur, causing surface distress.

Furthermore, an increase of air pressure within the alluvial pore spaces tends to decrease the injection rate of water into the porosity reservoir (i.e., gravity drainage of water is slowed due to the higher air pressure, and recharge wells must be run at a higher pressure to overcome the greater air pressure within the alluvial materials).

In addition to the above-described problems associated with entrapped air during the filling of the reservoir, the process of withdrawing water from the reservoir can cause the creation of a partial vacuum within the reservoir that inhibits or slows the further pumping of water from the reservoir.

As with entrapped air, a vacuum created within the alluvial pore spaces of the reservoir is not easily filled due to the substantially impermeable borders of the porosity reservoir.

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