Alternative Water Supply Options

Raw water, which is untreated water that can be used for non-potable uses, can be used as an alternative water supply that may reduce water treatment and distribution inefficiencies.  Raw water from local ditches and untreated groundwater supplies are used throughout the state for irrigation water, as well as other non-potable uses (e.g., the Town of Fowler has a dual water delivery system, with raw water plumbed to most residential and commercial customers for toilet flushing as well as outdoor irrigation uses).

Conjunctive use is the coordinated management of surface water and groundwater supplies to maximize the yield of the overall water resource. An active form of conjunctive use utilizes artificial recharge, where surface water is intentionally percolated or injected into aquifers during wet years or years with surplus supplies for later use. A passive method of conjunctive use is to simply rely on surface water in wet years and use groundwater in dry years, when surface lows are insufficient.

For those water utilities that have either trans-basin surface water supplies that can be used to extinction or non-tributary groundwater supplies water reuse involves capturing municipal wastewater return flows for new purposes (e.g., non-potable irrigation, potable water supply, etc.).

Many water utilities maintain an interconnection (or multiple interconnections) with other wholesale and/or retail water providers to allow for a sharing of water supply and to support improved system reliability.  Interconnects allow for redundancy in the supply system, a means to generate revenue when excess supply is available, and a means to expand water supply options during water scarcity.

Agricultural water is made available for lease as farmers fallow their land on a rotational basis or reduce the consumptive use of their cropping operations by limiting irrigation.  The water made available is then pooled (via the Super Ditch structure administered by the Lower Arkansas Water Conservancy District and then auctioned to municipalities and private water companies.

(Reproduced from Black and Veatch, 2010, “Arkansas Valley Conduit Pre-NEPA State and Tribal Assistance Grant (STAG) Reports,” Southeastern Colorado Water Conservancy District, Pueblo, CO.)

The exchange of water resources within the Arkansas River system in Colorado is dependent upon several integrated factors that include:

• Physical water supply that is available for exchange in time, amount and location at the intended points of diversion and storage.  For example, the amount of water allowed for temporary reservoir storage is limited to the amount of streamflow then present at the point of diversion into a ditch/canal or the return flows from a municipality that has been allocated Fry-Ark Project waters.  The physical water supply characteristics may also include the amount of storage space available in reservoirs that are able to capture the exchange water for subsequent release to the designated party in the water exchange(s), with inclusion of appropriate timing and transit losses between the point of release and application to beneficial use.
• Water is legally available for exchange in terms of its relative priority within the tributary stream system, in context of other water rights and other exchanges.  The exchange must also be in compliance with all other applicable Fry-Ark Project legal and policy instruments, including but not limited to, statutes of the United States, the State of Colorado, the Operating Principles, and the relevant Allocation Principles, Policies, and Resolutions adopted by the SECWCD.
• Administration of the subject exchange(s) by the Division Engineer, who may require additional information and notice such as the installation of adequate measuring devices or procedures to quantify the amount of municipal return flows claimed from Fry-Ark Project participants.  With an appropriate water court decree quantifying non-measured Fry-Ark Project return flows from a participant, it may be possible to exchange these return flows also.

There are two fundamental types of exchanges addressed in this analysis.  The first is the exchange of direct flow rights such as the exchange of irrigation water for municipal or domestic use.  An example of this potential exchange would be the exchange of a portion of consumable water available to a ditch/canal that is able to divert native Arkansas River streamflows in priority to serve a municipal use supplied by the AVC, including the assignment of applicable transit losses and carriage charges.  This type of direct flow exchange uses non-Project water and may occur in priority during the time when there is excess capacity available in the AVC and there is sufficient water to accomplish the exchange without harm or injury to other water rights in the system.

In all circumstances, the direct exchanges are subject to existing hydrologic conditions and must be approved by the relevant parties to the exchange, including the SECWCD and Division 2 Engineer.  Further, it will be necessary to quantify the consumptive use of water in the diversion structures associated with an exchange of water from downstream diversion structures up to the point of delivery to the AVC in Pueblo Reservoir.  To secure the long-term potential use of an exchange, it is necessary not only to quantify the historical consumptive use but also to adjudicate the water right exchange through the Division 2 Water Court for municipal and domestic uses.  The adjudication will also establish a priority date for the exchange.

The second type of exchange incorporates the use of reservoirs for temporary capture and release of water that was either (1) available for diversion from a stream system by a structure in priority, or (2) return flows from Fry-Ark Project waters as they accrue back to the tributary stream system.  Therefore, the types of water in storage that may be used for exchange may be either (1) non-Project water that is stored in Fry-Ark Project Reservoirs, if and when legal and physical storage capacity is available; or (2) Fry-Ark Project return flows from downstream Project participants. Consistent with direct flow exchanges, the use of reservoir storage must also be approved by the relevant parties to the exchange, including the SECWCD, Reclamation, and Division 2 Engineer.

It is important to recognize that all other institutional matters relevant to the delivery, use, and administration of any exchange of Fry-Ark Project water return flows or non-Project water using the AVC must receive authorization from appropriate SECWCD, state, and federal government officials prior to operations of said exchange.