Pipeline to close loop in Guadalentín Valley

Since May 2017, the Tagus-Segura Water Transfer line has been closed because water levels in the reservoirs of the upper waters of the Tagus (Entrepeñas and Buendía) have fallen below 400 Hm3, the minimum level at which water can be transferred. Part of the traditional irrigation area of the Lorca Irrigation Association, with a surface area of 3000 Ha, is served exclusively from: the Transfer line, water from the Puentes reservoir (which is expected to last until the end of April 2018) and low-quality flows with high conductivity from wells. For this reason, in October 2017, the Governing Body of the Lorca Irrigation Association requested the Association’s technical department to prepare a study, including estimated costs, of the feasibility of supplying this irrigable area with water from the Águilas-Guadalentín Desalination Plant.

Proposed solution

A water supply pipeline of 1200 in diameter carries water from the Águilas Desalination Plant. This line runs along the right bank of the Guadalentín Valley and provides the necessary flows of water for the consolidated irrigation area. This is the only irrigation water available to this area. However, the aforementioned supply problem affects the traditional irrigation area, which runs along the left bank of the Guadalentín valley.

Availing of the fact that there are two ponds for the storing and regulation of irrigation water, each with a capacity of 400,000 m3 and pipes to enable the water to be conveyed and supplied, the solution to the problem of lack of supply on the left bank was to build a pipeline to join the pipe from the desalination plant with the pipes and ponds on the other bank to enable both banks to be supplied.

Apart from solving the issue of lack of flows, this new pipeline also solves the problem of the poor quality, excessively saline water from the wells that supply these 3,000 hectares of irrigation land. It is now possible to mix the water from the two sources to obtain irrigation water of optimum quality. The fact that new pipeline can operate in both directions enables water to be taken from other sources to the consolidated irrigation area (Wells, WTTP, Transfer). Water from these sources is used in the traditional irrigation area and has a price per cubic meter considerably lower than that of desalinated water.

The Irrigation Association’s technical department submitted different proposals to the Governing Body for the construction of the pipeline. Choosing a route was a complex matter due to the numerous buildings in the area and the fact that the irrigable plots are very fragmented. After studying the different options, we believe that we have adopted the least damaging to owners, which has also resulted in a shorter pipeline, thereby minimising the cost and the execution period, which is important given the urgent nature of the infrastructure.

Once the route had been finalised, the first step was to request a longitudinal profile and a width of 50 m due to possible variations that might arise during the execution of the work. The second step was to signpost the width required for the installation of the pipeline by means of wooden posts in order to enable owners to see the route and the disturbance that it might cause them. The next step was to proceed to the modelling of the line using Epanet, with inputs of the flows we wished to convey and adjusting to the profiles and piezometric levels. It was decided to install a pipeline with a diameter of 800 mm and a length of 6,100 metres. The Governing Body was informed of this and requested an estimation of the cost of the work in order to ratify the proposal at the Ordinary Annual General Meeting in December 2017.

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Manuel Soriano Ibarra, Jefe de Obras de la Comunidad de Regantes de Lorca

Published in: FuturENVIRO #49 April 2018