Alternative Water Supply Options
The overall management of a water resources portfolio for any water utility includes balancing water supply with water demand. Any number of alternative water supplies may be available to a particular water utility depending on location, nature and character of their water rights, and the available market for water supply locally and regionally. Given the complex nature of water supply and water rights in Colorado, it will be incumbent on individual water utilities to evaluate their specific options and needs with respect to using and/or exploiting alternative water supplies.
The importance of alternative water supplies cannot be understated, especially in those communities with a growing customer base or diminishing available supplies. However, alternative water supplies have importance for all communities that are working to integrate the management of their water supplies and water demands, for excess water supply may be exchanged, leased or sold on an annual basis to members of the local or regional water community (or for organizations that are party to sharing of regional water supplies, local water demand reductions may support exchanges within the regional cooperative and/or reduce an operating expense). Alternatively, excess available water supply may be stored for carry-over from year to year, if adequate reservoir storage is available to a water utility. In this way, the benefits of water demand reductions and water use efficiency can be leveraged by creating more reliable water supplies in case of future water scarcity.
The specific types of alternative water supply options included in this Tool Box include:
Development and use of alternative water supply will require legal and engineering support, from the water utility, its partners and potentially the District.
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:
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.