It’s important to monitor the efficiency of systems that apply irrigation water in order to minimize waste from evaporation or over-application, but there’s another important type of waste that bears consideration. On an extremely simplified level, total water loss is estimated by calculating total withdrawals from a water source, subtracting the estimated consumptive use (evaporation, deep percolation, and evapotranspiration by and incorporation into, the plant), then subtracting the amount of water that is returned to the system.
While it’s not as obvious to the inexperienced eye, storage and conveyance inefficiencies usually represent a significant proportion of source water loss. We’ll discuss storage loss in our next section, but significant transportation losses can come from leaky pipes, insufficient capacity which leads to overflow loss, and, most often, seepage.
Water transportation on a farm is often by way of open canals that stretch from field to field or from irrigation point to irrigation point. Canals that are dug relatively deep compared to surface area will suffer less from evaporative loss, but unlined canals, regardless of their profile, often experience significant seepage. In most cases, water simply soaks into the ground along the length of the canal and eventually returns to the water table, where it must be pumped out once again.
Determining seepage in an unlined canal can be done through a technique called ponding. In a ponding test, a section of canal is blocked off at both ends and filled with water up to or slightly higher than the maximum water level. As the water level declines over time, measurements are taken and the time recorded, which are then used to calculate a seepage rate, after correcting for evaporation.
In cases where a seepage rate is high, farmers have options for reducing the permeability of their canals. Laying down a clay liner along the canal is one possibility; constructing a concrete canal system is another. Both options have their advantages and disadvantages, but other options exist which are superior in nearly all cases. Flexible geomembrane liners are significantly faster and easier to install than clay or concrete, and they are less permeable than these more traditional methods. There are plenty of geomembranes on the market, but the best, longest lasting and most reliable material is Reinforced Polyethylene (RPE), which offers flexibility, puncture resistance, welded seams and easy installation. The products available in BTL Liners’ AquaArmor Line are rated for potable water containment as well, which guarantees your canal liner won’t leach unwanted chemicals or additives into your irrigation water.
Repeatedly drawing water from underground and surface sources, then losing up to 30% to conveyance losses because of seepage, results in excess power costs and may even leave you in danger of exceeding your draw allowance if you’re in an area where those amounts are restricted. If your storage ponds and canals are unlined, drop us a line at btlliners.com and our expert team will be happy to discuss your needs and prepare a no-obligation quote.
