The Challenges are Here Today
In February 2022, scientists reported that the American West is currently in a megadrought, the worst that has been seen for 1,200 years. To put that into perspective, CE 800 was when Vikings sailed the North Atlantic and Mayans built temples across Mexico and Central America. The magnitude of this drought is devastating, considering the enormous increase in population relative to the last millennium, plus the regional warming effects of climate change.
The last 23 years have served as a wake-up call to farmers, ranchers, cities, and state governments as reliable freshwater resources, previously considered essentially infinite, have dried up or become too contaminated for use. Groundwater overdraft refers to the practice of drawing from underground aquifers beyond the rate at which it can be naturally replaced. The effects of this practice are catastrophic to our long-term access to clean water and cause serious short-term effects.
- Land subsidence is caused by decreasing water levels in vulnerable underground aquifers, such as those formed from a high percentage of clay. When the water table is depleted to the point where the clay is no longer saturated, the clay is compressed, the aquifer collapses and the land itself sinks.
Aquifer collapse and land subsidence cannot be repaired, and the storage offered by the destroyed aquifer is permanently lost. In parts of the San Joaquin Valley, California, land subsidence has affected over 5,000 square miles, with some dropping by as much as 28 feet. And the damage will continue. Studies from Stanford University have predicted the sinking may continue for 65 years and could even last for centuries. This is a major concern, since even minor incidences of land subsidence can cause repeated and substantial damage to infrastructure, including buildings, canals, roads, bridges, storm sewers, and utility lines.
- Energy requirements rise when water tables drop, and established wells run dry. If an aquifer is seriously depleted, farmers may be forced to drill new, deeper wells in a different location or even reach deep into fossil aquifers that were formed in earlier geologic periods. In the case of the Ogallala Aquifer, which occupies the High Plains of the US from western Texas to South Dakota, some segments are as deep as 1,000 feet below the surface.
As local resources dry up, farms, industry, cities and towns must transport water great distances to supply their needs. For example, California’s State Water Project is forced to move water more than 700 miles and nearly 2000 feet up and over the Tehachapi Mountains from Northern to Southern California.
- Non-renewable water supplies are increasingly tapped as water tables collapse, further limiting our future options. The Ogallala Aquifer, for example, is the largest aquifer in the US and was formed long ago. Fossil aquifers are no longer connected to the water cycle, meaning they do not refill and are therefore a limited, non-replenishable resource. At current withdrawal rates, the Ogallala Aquifer is expected to be 70% depleted within 50 years.
- Water quality problems often arise or are exacerbated when groundwater is drafted at a rate faster than it is naturally replenished. Existing pollutants, whether natural or manmade, are concentrated as the amount of stored water declines, making the contaminated water unsafe for drinking or even irrigation.
All groundwater naturally contains some level of dissolved salts and minerals from local geological formations, which can also render water unusable when they become concentrated enough. Agricultural runoff can make its way into overdrawn aquifers which supply drinking water for local communities. Exposure to high levels of nitrates present significant human health risks, especially to infants and young children. Industrial pollutants can enter groundwater through spills on land and release into local surface waters.
Treatment protocols could theoretically remove many of these contaminants, but the cost can be so prohibitive (reverse osmosis, for example) that it is considered impractical. They solution, then, depends on identifying alternative sources and closely managing withdrawals from existing aquifers.
- Surface Waters are inextricably connected to groundwater systems, so the depletion and contamination of groundwater inevitably affects rivers, streams, lakes, and the wildlife and plants they support. Critical wetlands habitats, economically valuable aquatic ecosystems, and even rest points for migratory birds may become contaminated or disappear altogether.
Even human interests are not immune: groundwater depletion has triggered conflicts over solar power plants, fish hatcheries, gravel mines, geothermal power plants, and more.
Into the Future
Unlimited use of freshwater resources across the globe is rapidly moving us to a crisis point, and it’s imperative that we develop and employ a variety of strategies designed to reduce our demands on limited resources and carefully husband and protect critical elements of the natural hydrologic cycle. Capture and reuse of water through strategies like stormwater harvesting, agricultural tailwater recycling, and green infrastructure planning can minimize the demands we place on both surface and groundwater, while practices like micro irrigation and the use of constructed wetlands to treat wastewater allow us to make the most efficient use of the water that we do have available.
The problems the world faces on a grand scale, from increasing scarcity of fresh, clean water, may be largely beyond the influence of individual farmers. Yet, the use of irrigation ponds to augment your water supply has beneficial effects not only for the ecology at large, but for the success of individual farm operations. We’ve already discussed the challenge of farming with ever-shrinking water allotments as well as increasing demands to limit agricultural runoff from polluting vulnerable surface waters. But what other benefits can an irrigation pond provide to your farm into the future?
- Frost protection water is often drawn from irrigation ponds, particularly for orchards and vineyards, saving farmers substantial money and allowing them to respond rapidly to changing weather forecasts.
- Wildlife habitats sprout up near reliable sources of water and you may find colonies of bees and other important pollinators have taken up residence, especially if you have undisturbed areas with native plant species.
- Flood Control is one of the most important benefits of an irrigation pond; like the detention and retention ponds used in cities that employ sustainable development practices. Severe storms, that dump water on developed land, can trigger deadly flooding as well as devastating erosion leading to mudslides, road collapse, and property damage. Irrigation ponds that capture, slow, and detain the flow of water through a watershed can diminish peak flows and minimize the effect of floods. As the climate continues to change and storms continue to increase in power, it may become common practice to install distributed networks of ponds which not only store larger amounts of water but also play a substantial role in protecting nearby properties and infrastructure.
Water for Fire Protection is rarely available in rural areas, especially when it is dominated by vast swaths of farmland. If a property is not located near a lake, reservoir, or substantial pond, firefighters may be significantly limited in their ability to control and extinguish a fire as they truck in and refill tankers, or set up a long connection of hoses to reach a pond that is a half mile down the road. Access to a nearby water source can make the difference between making repairs to a single building or rebuilding the whole operation from the foundations.
Even ponds as little as one acre-foot in size can contribute to fire protection if they’re relatively close to important structures. Substantial irrigation ponds obviously offer much more protection. Consider this benefit when you’re making decisions on where to site your ponds. It’s a good idea to consult your rural fire fighting team to find out how much storage is needed to adequately protect your property and consider their input when you’re designing the pond.
