As stormwater flows over driveways, lawns, and sidewalks, it picks up debris, chemicals, dirt, and other pollutants. Stormwater can flow into a storm sewer system or directly to a lake, stream, river, wetland, or coastal water. Anything that nters a storm sewer system is discharged untreated into the waterbodies we use for swimming, fishing, and providing drinking water. Polluted runoff is the nation’s greatest threat to clean water. By practicing healthy household habits, homeowners can keep common pollutants like pesticides, pet waste, grass clippings, and automotive fluids off the ground and out of stormwater. Adopt these healthy household habits and help protect lakes, streams, rivers, wetlands, and coastal waters. Remember to share the habits with your neighbors!
Healthy Household Habits for Clean Water
Vehicle and Garage
• Use a commercial car wash or wash your car on a lawn or other unpaved surface to minimize the amount of dirty, soapy water flowing into the storm drain and eventually into your local waterbody.
• Check your car, boat, motorcycle, and other machinery and equipment for leaks and spills. Make repairs as soon as possible. Clean up spilled fluids with an absorbent material like kitty litter or sand, and don’t rinse the spills into a nearby storm drain. Remember to properly dispose of the absorbent material.
• Recycle used oil and other automotive fluids at participating service stations. Don’t dump these chemicals down the storm drain or dispose of them in
your trash.
Lawn and Garden
• Use pesticides and fertilizers sparingly. When use is necessary, use these chemicals in the recommended amounts. Avoid application if the forecast calls for rain; otherwise, chemicals will be washed into your local stream.
• Select native plants and grasses that are drought- and pest resistant. Native plants require less water, fertilizer, and pesticides.
• Sweep up yard debris, rather than hosing down areas. Compost or recycle yard
waste when possible.
• Don’t over water your lawn. Water during the cool times of the day, and don’t let water run off into the storm drain.
• Cover piles of dirt and mulch being used in landscaping projects to prevent these pollutants from blowing or washing off your yard and into local water bodies. Vegetate bare spots in your yard to prevent soil erosion.
Home Repair and Improvement
• Before beginning an outdoor project, locate the nearest storm drains and protect them from debris and other materials.
• Sweep up and properly dispose of construction debris such as concrete and mortar.
• Use hazardous substances like paints, solvents, and cleaners in the smallest amounts possible, and follow the directions on the label. Clean up spills immediately, and dispose of the waste safely. Store substances properly to avoid leaks and spills.
• Purchase and use nontoxic, biodegradable, recycled, and recyclable products whenever possible.
• Clean paint brushes in a sink, not outdoors. Filter and reuse paint thinner when using oil-based paints. Properly dispose of excess paints through a household
hazardous waste collection program, or donate unused paint to local organizations.
• Reduce the amount of paved area and increase the amount of vegetated area in your yard. Use native plants in your landscaping to reduce the need for watering during dry periods. Consider directing downspouts away from paved surfaces onto lawns and other measures to increase infiltration and reduce polluted runoff.
Friday, May 29, 2009
Wednesday, May 27, 2009
Expensive Heat Pump Water Heaters
1 Heat pump 2 Temperature and pressure relief valve 3 Hot water outlet (to taps) 4 Back-up electric resistance heating element 5 Cold water inlet 6 Compressor 7 Refrigerant lines 8 Evaporator 9 Hot water storage tank 10 Heat exchanger 11 Drain pan
| ENERGY SOURCE | ELECTRICITY |
| MINIMUM EFFICIENCY RECOMMENDED | 2.0 EF |
| MAXIMUM EFFICIENCY AVAILABLE | 2.5 EF |
| EXPECTED LIFE | 11 years |
| ARROXIMATE COST TO INSTALL | $1,000-$1,500 |
Heat pump water heaters move heat from the surrounding air into the water. The heat pump is backed up by electric heating elements in the water tank for when demand outruns supply. Heat pump water heaters may be purchased as integral units with their own storage tanks (called one-piece systems), or they may be added on to electric-resistance water heaters. Heat pump water heaters are expensive, but they are a good alternative if electricity is your only available source of energy. They can save 25% to 45% of the cost of heating water with an electric-resistance heater.
Special Features
In a heat pump, energy is used not to generate heat but to move it, so a heat pump can have an Energy Factor above one. In fact, most heat pumps have EFs between two and three.
When heat pump water heaters move heat into the water, they cool and dehumidify the air surrounding the unit. This produces the equivalent of about 1/2 ton of air conditioning--which is helpful if your home usually needs cooling. But when winter comes, that cool air will put more demand on your heating system.
Precautions
Heat pump systems should be designed and installed by experts. One-piece systems require less design work and are simpler to install. Choose your contractor carefully.
Heat pump water heaters should be installed inside the house because they can freeze up if the temperature drops below 45°F. And they should be in an open, unconfined space, since they need lots of surrounding air from which to extract heat.
Heat pumps require more maintenance visits than most other systems. Depending on your water quality, the heat exchanger coils may need to be cleaned as often as every three months. This is not something most homeowners can do on their own.
Sizing
Heat pumps are slow. Most electric-resistance heaters can heat 20 gallons per hour. Heat pumps usually manage only 10 to 15. If demand exceeds supply, the inefficient backup heaters go on. While a larger storage tank can help you to avoid running out of hot water, it will lead to increased standby loss.
Like other storage units, heat pump water heaters are sized by first-hour rating. However, your contractor will also need to size the backup electric coil. Make sure the heat pump is sized to minimize use of the backup system.
Tuesday, May 26, 2009
Water Evapotranspiration and Transpiration
What is evapotranspiration?
If you search for the definition of evapotranspiration, you will find that it varies. In general, evapotranspiration is the sum of evaporation and transpiration. Some definitions include evaporation from surface-water bodies, even the oceans. But, since we have a Web page just about evaporation, our definition of evapotranspiration will not include evaporation from surface water. On this site, evapotranspiration is defined as the water lost to the atmosphere from the ground surface, evaporation from the capillary fringe of the groundwater table, and the transpiration of groundwater by plants whose roots tap the capillary fringe of the groundwater table. The banner at the top of this page offers an even more simple definition.
The transpiration aspect of evapotranspiration is essentially evaporation of water from plant leaves. Studies have revealed that transpiration accounts for about 10 percent of the the moisture in the atmosphere, with oceans, seas, and other bodies of water (lakes, rivers, streams) providing nearly 90 percent, and a tiny amount coming from sublimation (ice changing into water vapor without first becoming liquid).
Transpiration: The release of water from plant leaves
Just as you release water vapor when you breath, plants do, too – although the term "transpire" is more appropriate than "breath." This picture shows water vapor transpired from plant leaves after a plastic bag has been tied around the stem for about an hour. If the bag had been wrapped around the soil below it, too, then even more water vapor would have been released, as water also evaporates from the soil.
Plants put down roots into the soil to draw water and nutrients up into the stems and leaves. Some of this water is returned to the air by transpiration. Transpiration rates vary widely depending on weather conditions, such as temperature, humidity, sunlight availability and intensity, precipitation, soil type and saturation, wind, and land slope. During dry periods, transpiration can contribute to the loss of moisture in the upper soil zone, which can have an effect on vegetation and food-crop fields.
How much water do plants transpire?
Plant transpiration is pretty much an invisible proces – since the water is evaporating from the leaf surfaces, you don't just go out and see the leaves "breathing". Just because you can't see the water doesn't mean it is not being put into the air, though. One way to visualize transpiration is to put a plastic bag around some plant leaves. As this picture shows, transpired water will condense on the inside of the bag. During a growing season, a leaf will transpire many times more water than its own weight. An acre of corn gives off about 3,000-4,000 gallons (11,400-15,100 liters) of water each day, and a large oak tree can transpire 40,000 gallons (151,000 liters) per year.
Atmospheric factors affecting transpiration
The amount of water that plants transpire varies greatly geographically and over time. There are a number of factors that determine transpiration rates:
Transpiration and ground water
Diagram showing how the water table can dip where plant roots access it during the growing season. In many places, the top layer of the soil where plant roots are located is above the water table and thus is often wet to some extent, but is not totally saturated, as is soil below the water table. The soil above the water table gets wet when it rains as water infiltrates into it from the surface, But, it will dry out without additional precipitation. Since the water table is usually below the depth of the plant roots, the plants are dependent on water supplied by precipitation. As this diagram shows, in places where the water table is near the land surface, such as next to lakes and oceans, plant roots can penetrate into the saturated zone below the water table, allowing the plants to transpire water directly from the ground-water system. Here, transpiration of ground water commonly results in a drawdown of the water table much like the effect of a pumped well (cone of depression—the dotted line surrounding the plant roots in the diagram).
If you search for the definition of evapotranspiration, you will find that it varies. In general, evapotranspiration is the sum of evaporation and transpiration. Some definitions include evaporation from surface-water bodies, even the oceans. But, since we have a Web page just about evaporation, our definition of evapotranspiration will not include evaporation from surface water. On this site, evapotranspiration is defined as the water lost to the atmosphere from the ground surface, evaporation from the capillary fringe of the groundwater table, and the transpiration of groundwater by plants whose roots tap the capillary fringe of the groundwater table. The banner at the top of this page offers an even more simple definition.The transpiration aspect of evapotranspiration is essentially evaporation of water from plant leaves. Studies have revealed that transpiration accounts for about 10 percent of the the moisture in the atmosphere, with oceans, seas, and other bodies of water (lakes, rivers, streams) providing nearly 90 percent, and a tiny amount coming from sublimation (ice changing into water vapor without first becoming liquid).
Transpiration: The release of water from plant leaves
Just as you release water vapor when you breath, plants do, too – although the term "transpire" is more appropriate than "breath." This picture shows water vapor transpired from plant leaves after a plastic bag has been tied around the stem for about an hour. If the bag had been wrapped around the soil below it, too, then even more water vapor would have been released, as water also evaporates from the soil.Plants put down roots into the soil to draw water and nutrients up into the stems and leaves. Some of this water is returned to the air by transpiration. Transpiration rates vary widely depending on weather conditions, such as temperature, humidity, sunlight availability and intensity, precipitation, soil type and saturation, wind, and land slope. During dry periods, transpiration can contribute to the loss of moisture in the upper soil zone, which can have an effect on vegetation and food-crop fields.
How much water do plants transpire?
Plant transpiration is pretty much an invisible proces – since the water is evaporating from the leaf surfaces, you don't just go out and see the leaves "breathing". Just because you can't see the water doesn't mean it is not being put into the air, though. One way to visualize transpiration is to put a plastic bag around some plant leaves. As this picture shows, transpired water will condense on the inside of the bag. During a growing season, a leaf will transpire many times more water than its own weight. An acre of corn gives off about 3,000-4,000 gallons (11,400-15,100 liters) of water each day, and a large oak tree can transpire 40,000 gallons (151,000 liters) per year.
Atmospheric factors affecting transpiration
The amount of water that plants transpire varies greatly geographically and over time. There are a number of factors that determine transpiration rates:
- Temperature:Transpiration rates go up as the temperature goes up, especially during the growing season, when the air is warmer due to stronger sunlight and warmer air masses. Higher temperatures cause the plant cells which control the openings (stoma) where water is released to the atmosphere to open, whereas colder temperatures cause the openings to close.
- Relative humidity: As the relative humidity of the air surrounding the plant rises the transpiration rate falls. It is easier for water to evaporate into dryer air than into more saturated air.
- Wind and air movement: Increased movement of the air around a plant will result in a higher transpiration rate. This is somewhat related to the relative humidity of the air, in that as water transpires from a leaf, the water saturates the air surrounding the leaf. If there is no wind, the air around the leaf may not move very much, raising the humidity of the air around the leaf. Wind will move the air around, with the result that the more saturated air close to the leaf is replaced by drier air.
- Soil-moisture availability: When moisture is lacking, plants can begin to senesce (premature ageing, which can result in leaf loss) and transpire less water.
- Type of plant: Plants transpire water at different rates. Some plants which grow in arid regions, such as cacti and succulents, conserve precious water by transpiring less water than other plants.
Transpiration and ground water
Diagram showing how the water table can dip where plant roots access it during the growing season. In many places, the top layer of the soil where plant roots are located is above the water table and thus is often wet to some extent, but is not totally saturated, as is soil below the water table. The soil above the water table gets wet when it rains as water infiltrates into it from the surface, But, it will dry out without additional precipitation. Since the water table is usually below the depth of the plant roots, the plants are dependent on water supplied by precipitation. As this diagram shows, in places where the water table is near the land surface, such as next to lakes and oceans, plant roots can penetrate into the saturated zone below the water table, allowing the plants to transpire water directly from the ground-water system. Here, transpiration of ground water commonly results in a drawdown of the water table much like the effect of a pumped well (cone of depression—the dotted line surrounding the plant roots in the diagram).
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