Nature’s Drought Cycles Necessitates Better Water Supply Planning
News stories are reporting about Sarasota County’s “abnormal drought” or “below normal rainfall” conditions this year. These descriptions are catchy, but they’re also unintentionally confusing and may lead policy makers and planners to make critical miscalculations. The reports of abnormal weather conditions may present accurate data, “year-to-date rainfall is below an annual average,” but they lead the public into thinking that lower-than-average annual rainfall is an unexpected and atypical weather pattern.
Normal is something that conforms to a regular pattern or occurs naturally. Like most geological phenomena, weather is best understood when considered in terms of decades or centuries. While this year’s drought may appear “abnormal” when compared to last year, or even the last five or six years, it is perfectly normal in terms of the last 20, 50 or 100 years. In fact, the news accounts that described the droughts of 2000, 1980, 1971 and 1956, read just like today’s news.
Periodic severe droughts are not only normal; they are cyclical and relatively predictable. We will likely see another one, or maybe two, some time within the next ten years. What’s becoming abnormal is the environment’s ability to cope with these naturally occurring drought cycles. As the human consumption of water increases, more and more water is taken from our aquifers, lakes, rivers and streams. The ability for these natural systems to recuperate from prolonged droughts is diminished year after year. Even if we disregard the possibility of human-aggravated climate change, decades of over-pumping have clearly compromised the environment’s ability to recover from even naturally occurring droughts.
Water supply planners attempt to calculate water needs for human consumption and the environment by estimating the needs of both during a “1-in-10 year drought”. They estimate how much water is needed hypothetically to sustain a healthy environment and meet the demands of utility customers during a drought that occurs, on average, once every ten years. This assumption has recently raised serious questions that need to be addressed before water supply planning efforts and future growth decisions are made.
The best way to maintain an adequate water supply through a Southwest Florida drought is to store enough water during the rainy season to last through the dry season. Prolonged droughts present the greatest challenge to water storage strategies. This year’s drought proved too challenging, and our storage systems, designed to the 1-in10 year standard, failed to provide adequate reserves.
It’s convenient but unwise to think that 1-in-10 year droughts occur at ten year intervals. Weather happens in cycles. It’s reasonable to assume that we will get two 1-in-10 year droughts within a two to three year period. In fact multi-year or consecutive-year droughts are the typical pattern. Should the drought we had this year continue, or another prolonged drought occur before our reserve storage systems are restored, we’ll have a very serious problem.
Water from the Peace River, a critical regional water resource, is diverted during the rainy season and stored in a 500 million gallon lake and underground aquifers capable of storing an additional six billion gallons of water. Both of these reservoir systems were depleted this year, and the region found itself struggling to find emergency water sources to meet its demands. This struggle included relaxing permit conditions intended to protect the environment and pumping more water out of the storage aquifers than was pumped into them. It took four years to accumulate this stored capacity and only one drought to wipe it out. It’ll now take another three to five years to restore reserves to a “drought resistant” capacity.
Plans are underway to increase the storage capacity of the region’s water supply. A greatly expanded surface reservoir and additional aquifers will provide much needed relief. But we must learn from past mistakes and not allow the demands of growth to outstrip our ability to ensure an environmentally sustainable, drought-proof water supply for the future. A plan designed to meet the needs of a 1-in-10 year drought, may seem “normal”, but it has also been shown to be inadequate. We need to do better. We need a more realistic approach to drought-proofing our water supply system. And we need to recognize the limits of our natural environment’s ability to endure the pressures of growth and the demand for water that they create.