By: Denis A. Rochat, President

Rainwater harvesting, when integrated into land use planning delivers enormous economic and environmental benefits.   For instance, consider a five acre hayfield to be subdivided for 20 new homes. Prior to development the soil can absorb quite a bit of rain. Storm runoff has a natural path that drains first into a stream and thence to a river. Development though changes the properties ability to naturally absorb rainfall. Now comes new roads, driveways and thousands of square feet of impermeable roof surface.

Soon the first rainfall event occurs. Just a single inch over the five acres drops over 135,000 gallons of water in our subdivision. Formerly much of that water was absorbed into the soil. Now, repelled by impervious surfaces much of the runoff heads directly into the stream and then the river bringing with it culprits that cause big problems for you and me:


  1. Sediment can cloud the water and make it difficult or impossible for aquatic plants to grow.
  2. Bacteria can wash into swimming areas and create health hazards.
  3. Plastic bags, bottles, and other debris washed into streams can disable aquatic life such as ducks, fish, turtles, and birds.
  4. Household hazardous wastes, such as insecticides, pesticides, paint solvents, motor oil, and other auto fluids can poison aquatic life. Land animals and humans can become sick or even die from eating diseased fish or ingesting polluted water.
  5. Polluted stormwater can affect drinking water, which can affect human health and increase drinking water treatment costs.
  6. And waste from chemicals and materials used in construction can wash into the storm sewer when it rains.

This from a single disturbance of only five acres.  Now imagine a city being built along that river. Two more problems are created in addition to pollution. Now we can anticipate quantum increases in impact from water seeking a place to flow, i.e.:

  1. Erosion and Flooding. With all the hard surfaces of roads, houses, and buildings the river has to handle many, many times more runoff. This causes erosion of land and flooding.
  2. Depleted Groundwater. Much of the water that is now runoff used to be absorbed into the land and recharge the groundwater supplies.

Without development there is no growth and without growth there is no life.  This spoken by a guy with nine children.  Life and growth are highly attractive to me. Both come with responsibility for consequences. The ability to mitigate the stormwater consequences of land use is one of the major values of rainwater harvesting. This is validated by recent publications and seminars in which the Environmental Protection Agency  (EPA) has named rainwater harvesting as a tool to consider to achieve the goals of its newer and stricter water quality regulation- MS4.

So what’s the solution?

The EPA believes MS4 is the answer to correcting many water related consequences of land use.  MS4 stands for Municipal Separate Storm Sewer System (MS4). By definition an MS4 is a system of conveyances that include catch basins, curbs, gutters, ditches, man-made channels, pipes, tunnels, or storm drains that discharges into waters of the United States. An MS4 moves water away from an area to a local water body. MS4 is a 2 phase program. Phase I of the program focuses on large and medium sized cities above 100,000 population. Phase II zooms in on new developments of one acre or more. The MS4 directives are handed down to each state. In Tennessee, the Tennessee Department of Environment and Conservation (TDEC) is the permitting authority that has issued 84 permits throughout the state. The permitting program is designed to be tailored for each municipality. Permits are generally four years in duration and will normally be re-issued with more stringent requirements than the previous permit. However, the general idea is that the first inch of rain will not be allowed to leave a property that is developed after the enforcement begins in 2014. You are probably wondering if you read that right.  The first inch of a rainfall event will not be allowed to leave the property.  That’s right! How can that possibly be accomplished? Engineers, architects, and government agencies all over the country are wondering the same thing and scrambling to find methods for compliance.

Developments of the future will look much different. Pervious pavers, rain gardens, drip irrigation, landscape features, and rainwater harvesting.

Mitigating the problems caused by development is simply stewardship of the land.

  • Erosion and Flooding. Many problems causing erosion and flooding have been solved in Phase I of MS4. Many more will be solved in MS4 Phase II after 2014 by enforcement of stricter attention to containing runoff from construction sites and implementation of post construction runoff limitations.
  • Pollution. Much of the pollution problems can be mitigated by containing the first inch of a rainfall event on-site.
  • Depleted Groundwater. The current depletion of our groundwater supplies can be mitigated by utilizing landscape design that promotes absorption into the ground, using pervious pavers instead of asphalt and concrete, and utilizing groundwater recharge systems to introduce captured water back into the ground.

Development without mitigating problems will lead to polluted water, depleted groundwater, diminishing surface water, reduced plant and animal life, and scarcity of water for human existence. Many generations before us have performed ritualistic rain dances in desperate attempts to call down rain. We don’t have to dance for rain; we can dance in the rain.

Stormwater may, at first blush, seem to be a costly problem to eliminate, but it can be an asset to be acquired and used.

Rainwater Harvesting. Capturing and storing rainwater for use is unique among all the methods of achieving MS4 compliance. It captures all of the rooftop water, which is a significant portion of the hard surface of most developments. Secondly, and the best part, it can be used. It can be used for irrigation, potable water (residential applications), industrial processes, watering livestock and poultry, car and truck washes, and many more uses. No other method of compliance can eliminate runoff while providing multiple uses for the water. Further, inherent with using the water comes with a payback. A well-designed rainwater harvesting system includes 12 important elements in the process from rooftop to use.

So yes, rainwater harvesting can be a key element in land use planning.  It is a tool by which to control erosion, reduce pollution, and recharge groundwater. Ours is a deceptively simple technology with an important role in protecting our rivers, lakes, and streams.

Rainwater is not really a problem at all. It just depends on how you see it and how you manage it. It’s actually an asset. The oil of the future. It’s the best quality of water on earth just out of nature’s big distiller in the sky. That’s why we Celebrate the Rain!


Denis Rochat is the President of Rainwater Resources™ in Knoxville, TN.






From EPA website Construction: What types of construction activities are regulated under the construction stormwater permit program?

All construction activities 1 acre or larger must obtain permit coverage. Construction activities less than 1 acre must also obtain coverage if they are part of a larger common plan of development or sale that totals at least 1 acre. Small construction activities, i.e., less than 5 acres, may qualify for a waiver. For more information on the waiver see

What kinds of stormwater discharges are required to have NPDES stormwater permit coverage?

Operators of construction activity that disturbs 1 or more acres of land; construction sites less than 1 acre are covered if part of a larger plan of development

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