Numerical Canal Seepage Loss Evaluation for Different Lining and Crack Techniques in Arid and Semi-Arid Regions: A Case Study of the River Nile, Egypt

Owing to the potential negative impacts of climatic changes and the grand Ethiopian renaissance dam, water scarcity has become an urgent issue. Therefore, the Egyptian Ministry of Water Resources and Irrigation has started a national project of the lining and rehabilitation of canals, to reduce seepage losses and for efficient water resource management. This study presents a new approach for assessing three different lining and crack techniques for the Ismailia canal, the largest end of the river Nile, Egypt. A 2-D steady state seep/w numerical model was developed for the Ismailia canal section, in the stretch at 28.00–49.00 km. The amount of seepage was significantly dependent on the hydraulic characteristics of the liner material. The extraction from aquifers via wells also had a considerable impact on the seepage rate from the unlined canals; however, a lesser effect was present in the case of lined canals. The concrete liner revealed the highest efficiency, followed by the geomembrane liner, and then the bentonite liner; with almost 99%, 96%, and 54%, respectively, without extraction, and decreasing by 4% for bentonite and geomembrane liners during extraction; however, the concrete lining efficiency did not change considerably. Nevertheless, the efficiency dramatically decreased to 25%, regardless of the lining technique, in the case of deterioration of the liner material. The double effect of both deterioration of the liner material and extraction from the aquifer showed a 16% efficiency, irrespective of the utilized lining technique.

Groundwater Recharge to Address Integrated Groundwater and Surface Waters

The Eastern Snake Plain Aquifer (ESPA) Recharge Program aims to recharge an average of 250,000 AFY to mitigate the effects of groundwater pumping on surface water resources and, in doing so, to reduce conflicts between surface and groundwater users. The Idaho Water Resources Board (IWRB) partners with canal and irrigation companies to use IWRB’s surface water rights to conduct aquifer recharge through in- and off-canal seepage and direct injection wells. The canal and irrigation companies are paid by IWRB to use their canals and property for recharge sites. From 2014 to 2019, the program achieved 249,028 AFY of average recharge per year. The ESPA Recharge Program serves as a good example of a statewide recharge program that addresses challenges in managing highly connected groundwater and surface water. Moreover, it illustrates the incentives that can emerge for joint management of groundwater and surface water based on legal regimes that integrate the two. The ESPA Recharge Program particularly benefited from its centralized structure, with one state agency, IWRB, given sole control of implementing the recharge program. Nevertheless, the program faces some future obstacles, namely, in securing long-term funding, building out conveyance capacity to transport water to recharge sites during wet years, and modeling groundwater resources adequately.

An Experimental Study on Concrete and Geomembrane Lining Effects on Canal Seepage in Arid Agricultural Areas

Canal lining is commonly used to reduce seepage loss and increase water use efficiency. However, few studies have quantitatively estimated the seepage control effects of different lining materials under different service times. Ponding tests were conducted on the same canal section with four different lining statuses to investigate the canal lining effect on seepage control and its impact factors in arid areas. The cracks and holes in different lining materials were surveyed, and the canal seepage rates under the four test treatments were calculated by monitoring the water level change in the canal. The results show that the cracks in the joints of the two precast concrete slabs and holes in the geomembrane, which are located 0.25 m above the canal bottom on two sides of the canal, are responsible for the increased seepage loss. The new concrete and geomembrane lining combination reduces seepage by 86% compared with no lining, while seepage can be reduced by 68% using the concrete and geomembrane lining combination after three service years, and the amount decreases to 11% by using geomembrane lining with a three year service time. Based on the experiment and literature, a statistical relationship between the seepage reduction and lining service time was established, which provided a possible and easy way to estimate seepage losses from lined canals and improve the estimation accuracy using an empirical formula. Without considering the service time lining effect, the seepage loss is underestimated by 58%, and the canal water use efficiency is overestimated.

Evaluating a Water Conservation Response to Climate Change in the Lower Boise River Basin

Aquifers created or sustained by seepage losses from Bureau of Reclamation (Reclamation) Projects extend over vast areas of western states. Yet agricultural water conservation measures such as canal lining top the list of State and Federal policies for mitigating the effect of water shortages brought about by climate change. Cost benefit analysis (CBA) of new Reclamation water conservation infrastructure such as canal lining or piping is too often Project-specific, and detached from basin hydrology. The value of canal seepage as a positive externality is thus ignored in CBA. A basin-wide approach to hydro-economic modeling that accounts for the externalized costs and benefits of both canal seepage and new canal lining conservation insures that incidental aquifer recharge is recognized in CBA of Federally financed irrigation water conservation measures. Integrated hydrologic and partial equilibrium models are employed in the Lower Boise River basin to calculate the foregone benefit to non-project groundwater and drain water irrigation of a hypothetical Boise Project canal lining response to projected climate change water shortages. Basin-wide hydrologic response data is used to compute shifts in non-project groundwater supply functions and drain water supply constraints, and a base-case water supply scenario is compared to six climate change scenarios in which projected water shortages are offset by lining of project canals. The foregone net benefit to non-project groundwater and drain water irrigation resulting from elimination of the canal seepage externality (US$[Formula: see text]4.4–22.6[Formula: see text]million depending on the scenario) outweighs the increase in net benefit to Boise Project irrigation by canal lining (US$[Formula: see text]1.4–19.3[Formula: see text]million). On average, foregone groundwater and drain water irrigation benefit exceeds restored canal irrigation benefit by about 38%. Canal lining conservation is unable to restore total basin-wide irrigation net benefit to the base-case level in any of the climate change scenarios; rather it shifts the foregone benefit of climate change shortages from project canal irrigation to non-project groundwater and drain water irrigation. The canal lining CPA is not a complete accounting of either costs or benefits of canal lining conservation. On the cost side, only the foregone benefits of eliminating the positive canal seepage externality are calculated; construction and maintenance costs of canal lining are omitted. On the benefit side, Arrowrock canal irrigators are assumed to be the sole beneficiary of reduced seepage losses.