Dr. Robert W. Puls, Director
Oklahoma Water Survey
Some water Facts:
- The earth is covered with water but only about 3% is fresh water, meaning drinkable or potable
- Of that 3%, 2% is tied up in snow and ice
- The remaining 1 % is in lakes, reservoirs, rivers, wetlands, and ground water
- 7,000 years ago, water shortages spurred humans to invent irrigation
- Fresh water withdrawals have tripled over the last 50 years
- Population growth
- Consumption increase
- Energy demands
- USGS estimates for 2005 indicated 41.5% and 37% of water uses were for thermoelectric power and irrigation and 8.5% for domestic use.
- Water on earth is finite and constant. We have the same amount today that we had thousands of years ago, but reductions in fresh water can occur due to water contamination.
- Current domestic water use per person per day ranges from 60 to 180 gallons in the US (http://www.epa.gov/watersense/our_water/tomorrow_beyond.html) with less per capita usage in the east and more in the west. Oklahomans use about 80-100 gallons per day.
- Population growth in Oklahoma is projected to increase from approximately 3.7 million to 4.8 million by 2060 (OCWP, 2012)
The Water Cycle
The water cycle or hydrologic cycle on earth involves the continuous transfer of water via evaporation, condensation, precipitation, movement over the land surface and infiltration. Water evaporates from the oceans and other open water bodies, moves across sky as water vapor in clouds, condenses and returns to earth as rain and snow, and then returns to the oceans and other open water bodies through rivers and underground pathways to start the cycle again. Some of the water that falls on the land evaporates from the soil or is transpired from plants back into the atmosphere. Water flows overland to stream channels, lakes, or the sea. Water infiltrates through soils and then resides in an unsaturated zone where it exists or in a saturated zone. It is this latter component that is referred to as ground water.
Oklahoma’s Water Needs
Like most locations, Oklahoma’s demands for water will increase as population increases. The Oklahoma Comprehensive Water Plan (OCWP), 2012, projects about a 28% increase in water demand for the state by 2060 (Figure 2). The state legislature passed the ‘Water Act for 2060’ in 2012. This law establishes a statewide goal of consuming no more water in 2060 than is consumed now. To achieve this goal, we must use our existing supplies more efficiently, find new supplies and establish more efficient infrastructure to limit leakage and waste. Increased conservation and efficient use and water management practices will be essential to realizing this goal.
In response to the pressures of population increases and urban growth together with the potential for more severe and more frequent droughts, it is increasingly challenging to solve our water supply needs. Developing new water sources and interbasin water transfers is one approach, but alleviating demand may be more cost effective. This can be done through conservation, recycling and reuse.
Clearly the largest users of water are the agricultural and municipal/industrial sectors, however the growth rate would appear to be greatest for the oil and gas and thermoelectric power sectors. The good news is that these two sectors could make use of alternative sources of water to satisfy their needs. Non-fresh water sources (>5000 total dissolved solids [TDS]) or marginal waters could be used. Ground waters of over 5000 TDS do not require a permit for withdrawal in Oklahoma. There would be no competition between agricultural uses and municipal and rural drinking water supplies. Movement in this direction is already happening. Oil and gas industries in Oklahoma and elsewhere are increasingly using recycled or other marginal water sources in their operations. This is a relatively new practice but one that should be encouraged. Likewise, power plants are turning to marginal water sources for cooling needs (e.g., Luther and Newcastle, OK).
Reductions in potable water usage in agriculture and municipal/industrial sectors can also be achieved via reuse strategies. While the Oklahoma Water Act for 2060 addresses the general issue of conservation, it is noteworthy that the Oklahoma Department of Environmental Quality (DEQ) recently promulgated specific guidance for water reuse in 2012 (http://www.deq.state.ok.us/rules/627.pdf). In Title 252, Chapter 627, DEQ defines “Reclaimed water” as wastewater that has gone through various treatment processes to meet specific water quality criteria with the intent of being used in a beneficial manner. The Guidelines establish five categories and outlines permitted uses for all but category 1. Such water can be used for irrigation of golf courses, public use areas (e.g. sports complexes), toilet and urinal flushing systems, irrigation of livestock pastures, subsurface irrigation of orchards and vineyards, and restricted access landscape irrigation to name a few of the beneficial uses. There is no mention of potential reuse of treated wastewater for indirect potable water supplies; presumably this is restricted to category1.
Some states now allow reuse for indirect potable water supplies under certain restrictions and conditions. As might be expected, these are areas of the U.S. experiencing serious water supply shortages. Treated municipal wastewater is of a much higher quality than it was 20-30 years ago and often superior to the quality of the rivers and streams where it is discharged. The North Texas Municipal Water District (NTMWD) diverts return flows from the East Fork of the Trinity River, contributed by NTMWD-owned or customer-operated wastewater treatment facilities through a constructed wetland prior to delivery to Lavon Lake for subsequent treatment for drinking water use.
Water Conservation and Leaks
As Figure 1 illustrates almost 14% of domestic water usage is lost to leaks. Recent studies have shown that typically a small number of homes are responsible for the majority of the leakage: 105 of the homes were responsible for 58% of the leaks found (http://www.allianceforwaterefficiency.org/residential-end-uses-of-water-study-1999.aspx). Obviously this has implications for the water bills for those homes. The use of water monitoring devices on supply pipes would help identify these leakers. It should also be possible to identify these homes based on historical trends in water usage by either the homeowner or the utility.
Water losses also can be significant in public supply systems, particularly those with aging infrastructure. It is estimated that 7 billion gallons per day across the country are wasted due to leaking pipes (American Society Civil Engineers, EPA). This is treated water that costs about $2.6 billion per year. 30% of pipes in systems serving more than 100,000 people are between 40 and 80 years old. This aging infrastructure problem is ubiquitous regardless of regional location. Some areas are worse off due to age (Midwest, Northeast). The longer we wait to address this issue the more it will cost.
A recent report by the American Society of Civil Engineers (ASCE) found that improvements for aging water infrastructure could cost U.S. businesses $147 billion over the next decade. The report identified the following business sectors as absorbing the brunt of the impact: retail, restaurants and bars, and construction businesses. These economic impacts could be reduced if households and businesses adopt more sustainable approaches to water usage and management.
Water Conservation and Equipment Changes
As indicated above, toilets are a major drain on our water usage. First, why are we even using treated potable water to flush our toilets? Captured rainwater and other sources or non-potable water would do the job just fine. Older toilets, those most commonly used, require 3-5 gallons per flush. New, low flush toilets use than 2 gallons. Many communities now require these more efficient toilets in new homes and buildings. Clothes washers are also heavy users of potable water requiring 40 gallons per load; newer ones use than 25 gallons. There are also restricted flow faucets and showerheads available that can save water. Many cities provide ‘conservation kits’ for minimal cost to address some of these changes.
Other ways to save water include taking showers instead of baths, taking shorter showers, running dishwashers and clothes washers only when completely full, and capturing rain water for gardening and lawn irrigation. Many communities have programs to provide rain barrels at cost or low cost (http://www.clevelandcountyconservationdistrict.com/).
Water Conservation and Landscaping
There are a number of turfgrass varieties available that need less water or are drought tolerant. Perhaps as important as choosing the right variety of grass to conserve water is the strategic placement of turf, irrigation systems, and hard impervious surfaces. Systems should be designed to avoid watering of hard surfaces, thus losing valuable water to runoff and storm drains. For existing irrigation systems, yearly adjustments are recommended to avoid watering hard surfaces. Sensors are available so that irrigation does not occur during rainfall events. Texas A&M University (http://urbanlandscapeguide.tamu.edu/waterwise.html) has produced a guide to a ‘WaterWise Landscape’. It involves the following seven principles:
- Appropriate plant selection
- Planning and design
- Soil preparation
- Practical turf areas
- Efficient irrigation
- Use of mulches
- Appropriate maintenance
Xeriscape is a term that applies to low-maintenance landscapes requiring less water. These are water-efficient landscapes that can be designed according to local geographic and climatic conditions. The use of native plants is not necessary but certainly worthy of consideration. Oklahoma State University maintains a site (http://osufacts.okstate.edu/docushare/dsweb/Get/Document-6994/L-333%20Xeriscape%20plants.pdf) that provides a listing of different xeriscape plants including trees, shrubs, groundcovers and grasses. Xeriscape is gaining in popularity as certain regions that increasingly experience drought conditions and communities face mandatory watering restrictions.
Figure 3. Lake Hefner, January, 2013
The Path Forward
It is not too late to begin planning for a future more dependent than ever on water but having less fresh water than we have grown accustomed to having. Conservation of the water we have will need to play a larger role in meeting our future needs. To make this work, we need to change our current thinking about the value of our water resources and how we conserve and efficiently use those resources and make changes to our laws and management strategies to more effectively meet this challenge.