Water is a major natural resource, one of the big three: land, water, air. Water is used in many ways - e.g., as a nourisher of plant and animal life, a bearer of food, a prime element of industrial processes, and a medium for transportation. The importance of water can be put into perspective by the fact that a significant portion of the earth's surface is water. When our planet is viewed from space, the dominant blue color makes water appear to be an abundant resource. The reality is that 97% of the earth's water is salty, and the majority of the under 3% that is freshwater is locked in glaciers and polar ice caps.

The freshwater pool on which we are most dependent is the resultant run-off of a water cycle driven by the sun. Evaporation lifts purified water from the oceans and land, which then falls again as rain and snow. Our backup reserves of freshwater is held in underground aquifers, but are energy intensive to extract from and slow to replenish. As is often the case with natural resources, a major problem arises from the uneven distribution, while others receive scant amounts. In some environments this imbalance is exhibited in just a few surface miles.

Worldwide population growth (and associated food production) as well as increases in industrialization and consumptive lifestyles create ever-increasing demands on the planet's relatively finite sources of freshwater. To ensure a global water resource to meet the demands of the future, immediate improvements are need in techniques for water conservation, collection, storage, treatment, and reuse.

Sustainable design will respect the water resources with diligence whatever the natural distribution. The challenge of sustainable design applies more to areas where freshwater is not limited than to dry areas (economics of high-cost water tends to promote wise stewardship). The principles of sustainable design apply, without reservation, to all types of climates. In an park or tourism development, where health considerations are paramount, water issues center on providing safe drinking, washing, cooking, and toilet flushing water.

STRATEGIES FOR SUSTAINABLE DEVELOPMENT

Water Conservation

The cornerstone of any domestic water supply program is conservation. Water conservation also includes using water of lower quality such as reclaimed wastewater effluent, gray water, or runoff from ground surfaces for toilet flushing or irrigation of vegetative landscape or food crops. These uses do not require the level of water quality as that needed for internal consumption, bathing, or washing. With the proper type of wastewater treatment and plumbing hardware, sea water can be used as a toilet flushing medium.

User education and awareness is a key to a successful water conservation program. At a resource-related development, the visitor should receive interpretation about the source of the water and the types of energy required to process and distribute the water at the development. If an offsite utility provides water, the same type of information must be obtained by management and furnished to the visitor, along with a description of the water conservation measures being used.

Positive reinforcement should be provided to visitors by estimating water savings and outlining their responsibilities in achieving the goal. Appropriate signs should be put in restrooms or bathrooms to confirm goals and expected behavior. Such signs should be of high quality material to indicate that management places high priority on water conservation.

Flush toilets are the largest inside user of water. To conserve water, the maximum permissible water use per flushing cycle is 1.6 gallons. Water conservation flush toilets are widely manufactured. Characteristics that should be evaluated before purchasing a low-flow toilet include operational noise, solids evacuation, bowl cleaning, and water surface seal area (water standing in bowl after flush cycle; i.e., the more water surface area the less cleaning of skid marks may be required). Double flush units also save water by providing a partial flush for liquid wastes and a complete flush (1.6 gallons) for fecal wastes. In some environments, waterless toilets such as composting toilets may be appropriate (see "Waste Prevention" for more discussion on composting toilets).

Lavatory fixtures should be spring-loaded and have a maximum flow rate of 2.2 gallons per minute (gpm) at a test pressure of 80 pounds per square inch (psi). Although most water systems operate in the 25-40 psi range, the high test pressure ensures that a purported conservation device actually does conserve water over a wide pressure range. Electronic proximity devices are now commercially available with lavatory fixtures. These units are water efficient but should be used only after evaluating local repair capabilities.

Shower fixtures should be rated for a maximum flow rate of 2.5 gpm at 80 psi. Shower fixtures of 2.0 and 1.5 gpm are available and work very satisfactorily depending on user preference. Shower fixtures should have a timed cycle after activation by user or be spring loaded with chain operator. Instead of a hot water shower, tempered water using a solar thermal collector may be a good median between a cold shower and an energy-intensive hot shower.

Urinals should have a maximum flow rate of 1.0 gpm and be spring-loaded.

Commercial appliances used in kitchen and laundry areas should also be water-savings models. Garbage disposals should not be used as they are water consumptive and exert a huge load on the wastewater treatment facilities. Park and ecotourism visitors typically are not be in direct contact with the kitchen, laundry, or other centralized facilities, so water conservation efforts in these areas should be part of the interpretive program of the development.

In areas having lodging facilities, check-out time or perhaps at the mid-point of a week-long stay is a good opportunity to let visitors know how much water was saved using conservation devices versus conventional devices. This does not need to be an actual measured volume but can be a computer-generated figure based on length of stay and number of visitors in the room. Also, a list of manufacturers and suppliers of water conservation and other energy savers should be made available so that visitors can take it home and use it in their everyday lifestyles. A nice touch would be a reusable or recyclable card to departing visitors reiterating management's pledge to the environment and offering a tangible object of this pledge such as a faucet aerator.

Water Sources

Groundwater (Wells and Springs). An uncontaminated groundwater source or spring usually requires the least input (energy, chemical, financial) to provide safe water for drinking, bathing, and cooking. Extreme efforts should be made to protect existing and potential groundwater sources from contamination. To ensure that groundwater is not contaminated by surface water or other influences, wells should be a minimum of 50 feet deep and generally 200 feet horizontal from surface water (see figure??).

Use of groundwater is probably the least energy-intensive because renewable energy sources (wind, photovoltaic) can be used to pump the water to a hillside storage reservoir for distribution by gravity. This type of system has so many advantages from both an environmental and economical perspective that the source can be developed up to several miles from the final use point.

Surface Water (Fresh). Fresh surface water can be used when groundwater is not available. Some locations have an abundance of fresh surface water such as streams, rivers, and lakes.

Lack of Groundwater or Surface Water. In those cases where there is a lack of water, rain catchment becomes an option as a stand-alone supply of water or a supplement to a limited ground or surface supply. Rainfall catchment from the roofs of structures is a recognized option for water supply, provided the necessary treatment processes are used prior to distribution. Care should be used in selecting a roofing material (e.g., hard and smooth) that does not collect dirt. Metal roofs may release heavy metals into the drinking water if the rainwater is acidic. Rainwater collected from ground surfaces (parking lots, etc.) can be used for secondary uses such as toilet flushing and irrigation of food crops.

Extraction of Freshwater from Sea Water, Brackish Water, or Water Vapor in the Air. Some areas have no readily available supply of freshwater and must rely on converting salt water to freshwater. Reverse osmosis, electrodialysis, distillation, and vapor compression are processes used. All are complex, extremely energy consumptive, costly, difficult to operate and maintain, and present significant disposal problems caused by the brine concentrate. It is probably beyond the means and capabilities of most small park units or sustainable developments to produce freshwater from salt water. The scale of most desalinization plants is very large. The fact that freshwater produced from salt water is very precious needs to be emphasized to visitors at every opportunity because the cost is just a fraction of the environmental cost. An example of how far-reaching the costs are is that energy used at the St. Johns, Virgin Islands, desalinization plants is produced by hydrocarbons from Alaska.

Whatever the water supply, information on the source of water used must be made known to users. This information can be transferred through interpretation (as part of the orientation packet, slides at evening shows, or a scheduled tour of the facilities once per week). The tour would be especially appropriate if sustainable water processing or pumping techniques are being employed.

Water Treatment

The type(s) of treatment required will depend on the source of water and the quality of source water.

Groundwater. Treatment of groundwater is accomplished by simple disinfection using sodium hypochlorite (laundry bleach). The sodium hypochlorite can be proportioned into the water being delivered to the storage tank using a wind-powered or photovoltaic metering pump. Contact time in the storage tank is required to ensure proper disinfection.

An emerging water disinfection technology involves the use of liquid chlorine dioxide (Aqua Chlor). This technology provides excellent bactericidal qualities while minimizing the formation of environmentally harmful disinfection by-products.

Surface Water with Low Turbidity. Before disinfection, surface water requires filtration. For resource-related developments, the recommended filtration processes would be slow sand filtration or cartridge filtration. Only the water used for drinking, washing, and cooking would need to be completely treated. Dual distribution systems are required - one for drinking water and one for lesser quality uses such as toilet flushing.

The slow sand filter is an old technology that has recently reemerged. An even graduated natural sand (3 feet deep) is placed in a constructed basin. The supply water is introduced into the top layer of sand and travels downward through the sand filter to perforated collection pipes on the bottom of the filter. Impurities in the water are removed in the top layer of the filter and accumulated for periodic removal by scraping. The removed impurities and top 1/2-inch of sand can be dried and used as a soil conditioner. No chemical additions or additional power are required. Operations and maintenance requirements are low. However, a certain land area is required for the filter basin. Figure ?? depicts the general relationship between land area for treatment versus complexity/cost of operations and maintenance. Disinfection with bleach is the final step.

Cartridge filters using microporous filter elements (ceramic, paper, or fiber) with small pore sizes are suitable for low turbidity surface water. (Use a graduated series of cartridge sizes to prevent rapid clogging of filter.) Again, a dual distribution system is recommended to lessen the volume of high quality water needed. Head loss through a cartridge filter is higher than through a slow sand filter, so a booster pump may be required to maintain adequate pressure in the water system. The paper and fiber filters are consumptive as they must be disposed when full of sediment (disposal frequency depends on turbidity in supply water). The ceramic cartridge filter can be cleaned mechanically (scrapping) and reused. Sediment cleaned from the ceramic cartridge can be dried and used as a soil amendment. Operations and maintenance is minimal. Disinfection with bleach is the final step.

Surface Water with High Turbidity. If the source water has a turbidity above 15-20 NTUs (nethelometric turbidity units), complete conventional treatment is required. This involves the addition of synthetic chemicals such as alum and polymer in a coagulation stage, followed by a flocculation stage before filtering in a rapid sand filter. The filter is hydraulically backwashed (usually once per day) to remove accumulated sediment from the filter. This backwash waste (containing the added chemicals) must be dried and disposed of in an approved manner. The complexity and cost of operation is high, maintenance costs are high, and chemical and power inputs are required. Dried waste sediments cannot be used as a soil amendment without further processing. The final step is disinfection with bleach.

Water Storage

Gravity storage of any water product (raw, finished, reclaimed) should be used wherever possible. For every 1 foot of elevation a storage tank is located above a use point, 0.433psi static pressure is generated (see Figure ??). Gravity storage enables wind and photovoltaic pumping systems to be effective. Because these pumping systems work at relatively low pumping rates, the gravity storage tank acts as an accumulator to store water for heavy demand periods or for days when the wind does not blow or the sun does not shine. Photovoltaic pumping systems can provide moderate daily flows of up to 25,000 gallons per day and produce total dynamic heads of 100-150 feet.

Another means of transferring raw water from a source to a storage tank at a higher elevation without electrical or hydrocarbon input is the hydraulic ram. The hydraulic ram is a self-acting impulse pump that uses the momentum of a slight fall of water to force a part of the water to a higher elevation. A hydraulic ram is noisy, but the noise can be successfully mitigated with the use of sound-attenuating materials in an enclosure. It is practicable to operate a ram with a fall of only 18 inches, but as the fall increases, the ram forces water to proportionately greater heights. The hydraulic ram is well suited for areas where electrical power is not available and where an excess supply of water is available.

As a gravity storage tank will be located in an elevated location, visual quality will be important. Multiple smaller tanks may be easier to screen than one large tank. Multiple tanks also provide greater flexibility in operation. Tank materials should be noncorrosive and sectioned for minimal transportation requirements to the tank site.

Water Distribution

Most distribution systems are either buried or placed at grade. At-grade distribution systems affect the site and vegetation minimally during construction. Burying has the advantage of protecting against accidental breakage, but leaks are more difficult to locate on a buried distribution system. Leak detection and repair is imperative when dealing with such a precious resource as water.

Dual distribution systems are very effective in that different qualities of water can be delivered to different use points. Pipe contents should be color coded so that cross-connection problems can be prevented.

Other Water-Related Amenities

Water should be allocated to the highest use. Degradation of water quality in activities not associated with higher water uses are not part of sustainable design.

Regulations

The World Health Organization and individual countries and associations all have health regulations governing drinking water. For many parameters the maximum allowable contaminant levels are not identical. A resource-related development should determine applicable regulations prior to initiating a water supply program.