The proposed 1.0 Pipeline would consist of 3,593 feet of 24-inch PVC pipe. The pipeline would replace inadequate irrigation service to 172 acres and improve service to an additional 162 acres south of Highway 281 and east of the Main Canal. The 1.0 Pipeline would provide an improved service of 3 cfs per individual turnout. This service is based on the assumptions that a typical turnout services 40 acres and 1/3 of farmers irrigate simultaneous. The proposed pipeline was designed under gravity flow conditions and will not require a pump station. The total cost of $96,500 for the 1.0 Pipeline includes construction costs, easement acquisition costs, and design costs.
The following provides a feasibility study for the construction of a 3,593-foot irrigation pipeline originally identified the pipeline as part of a potential distribution system improvement project in a 1993 engineering study. The study was performed to update rehabilitation work performed in the 1960's by the Bureau of Reclamation under Public Law 86-357. The intent of the proposed pipeline was to improve the irrigation supply to the 0.6 Pipeline. This feasibility study presents a hydrologic and hydraulic analysis used to design the proposed pipeline and a preliminary cost estimate. The proposed pipeline is referred to in this report as the 1.0 Pipeline.
The proposed pipeline will be modelled in this analysis using EPANET. EPANET is a computer program that performs extended period simulation of hydraulic and water quality behaviour within pressurized pipe networks (Anaya, 2004 65).
. The creation of the EPANET model involves defining the water supply source, the pipeline layout, the amount of available hydraulic head, the service area, the design flow rates, and the pipeline material and size (Bluntzer, 1992, 130). These parameters are described in the following sections.
Water Supply Source
The proposed 1.0 Pipeline will receive irrigation water directly from the District's Main Canal. The Main Canal conveys water from the La Feria Pump Station located on the Rio Grande River north 5.4 miles to the District's 2,000 acre-foot storage reservoir.
The 1.0 Pipeline will connect to the District's Main Canal approximately one mile north of the La Feria Pumping Plant. The pipeline will extend east approximately 3,593 feet from the District's Main Canal bisecting existing farmland and eventually connecting to the existing 0.6 Pipeline tract. The 1.0 Pipeline layouts was originally delineated in the 1993 Siger, Winston, Greenwood and Associates, Inc. engineering study.
The amount of hydraulic head available from the water source is an important variable in determining if the proposed pipeline can be designed and operated using gravity flow. The available hydraulic head represents the difference between the normal irrigation water surface elevation in the water supply and the natural ground elevations at the individual turnouts. A Trimble 5700 receiver was used to determine these elevations. The elevations are based on the NAD 1983 (Conus) datum.
During irrigation, the water surface elevation in the Main Canal is raised through the use of a check structure located just north of ...