Friday, July 24, 2009

Potable Water in The Woodlands, Texas - declining reserves explained

Over the past few years, we have been able to watch our rapid growing county gradually become water-deprived. That has happened for a number of reasons - high consumption per capita, rapid growth of population, and drought. We are dependent on subsurface reservoirs that are being depleted and not sufficiently recharged. Although the available amount of water is stressed, we are theoretically not short of water, ..... YET. The county is predicted to double in population in just a little over 10 years. That will cause huge problems for us. Therefore, our water utility districts are planning a major project to obtain, transport and replace our MUD wells (which are not even paid for yet) with surface water from Lake Conroe. This will occur only in the five major population areas of the county. Those living outside of those areas will keep their water wells and continue to utilize existing underground supplies.

The primary issue as has been described to me by James Stinson, General Manager of Joint Powers Agency, is the waste. He has publicly stated this several times. Residents are putting millions of gallons of our limited underground water on the street, in gutters. They are also utilizing much more than actually needed to water their lawns. Some lawns are watered even when it is raining. I have neighbors who do that. They are away and have their sprinklers programmed to regularly water the lawn on certain days. Of course they reprogrammed their system for the nighttime to conform to restrictions, but if it rains (which it has not), their water system does the same as when it is dry. Now if that is not waste, I don't know what is. This can be avoided by acquiring a rain monitor device that will shut off the automatic watering system when it rains. The JPA will even help you purchase one by rebating 50% of the cost up to $150. Most residents from what I have been told, measure what they put on the lawn; they simply water it until the ground is soggy. Usually ground is never soggy with proper watering techniques, because one inch delivered evenly will not cause soggy soil unless the soil is composed totally of a soft non-compacted dirt. It usually has plenty of sand and clay making it moderately soft even when moderately wet. I have never seen it "soggy" except when using soft dirt on the surface. So the GM says we waste 40% of our water and I can certainly believe that number! Please measure the water you deliver to your yard and restrict it to about one inch per week.

I measure mine with little tins from cat and dog food. I put a ruler into the water after watering and adjust my watering technique to make it about one inch everywhere in the sunny part of the yard and a little less in the shady spots.

What happens to the underground reservoirs when we deplete them faster than we recharge them? Down in the depths of the ground, there are producing water zones. These are composed of rock, usually limestone or sand, with a lattice structure to permit the retention and movement of water within them. The rock structure essentially is composed of billions of little cavities held together by lattice rock structures. Water moves into these zones from the surface when it rains, gradually seeping deeper and deeper into the soil until it reaches these underground "homes" for water. It forms an underground water network pulled by gravity. The water acts as a cushioning mechanism, keeping the lattice structure from collapsing. There is tremendous overburden pressure caused by the combination of gravity and the weight of the rocks and soil and everything else above it. When you take the water out of the structure at a faster rate than it is put into it, the water level drops, just like a river. The upper part of the structure then collapses or shrinks until it reaches a pressure equilibrium with the tensile strength of the rock lattices. When the structure collapses, it is gone forever. The space that once existed to hold water is gone. This causes subsidence and lowered capacity of the producing reservoir, just ask people in Harris County what happened in prior decades because of their depletion of the reservoirs! Also when structures collapse, there is no more underground water at that depth, requiring some people and some utility production wells to be deepened in the reservoir to reach the water supply. Thus the vicious cycle continues.

Here in The Woodlands, we have an opportunity to decrease the rate of this self destruct mechanism by not blatantly wasting our water. We utilize more than the rest of the county. We are upstream from Harris County and they produce from what we don't. We are in their recharge zone, which without much rain, has been a very limited or non-existent process in some areas lately, so what we do affects them. Water is a very precious and limited resource. We must invest in tools and time to conserve it. Every human being upon this earth has the responsibility, as custodians, to care for it.

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