The movement of moisture through a community or landscape has certain universal elements. The water enters from a high point as precipitation or runoff. Frequently there is concentration of sheet flows to channelized flows. Moisture is stored in soil, bodies of water and in organisms. Water exits at a low point as channelized flow, or it returns to the atmosphere as evaporation. When humans create water systems these elements become challenges of sourcing, consumption, and return flows.

Human systems differ from natural systems in a number of ways. Water is diverted and concentrated in the oases of cites and towns. It runs up hill driven by money and pumps. The natural hydrology is replaced by systems with higher velocities and reduced capture of moisture. These changes create interesting metaphors. Once there were perennial streams on the surface, fed by precipitation, infiltration and slow lateral flows. Now, in many urban areas, there are ephemeral streams in gutters, storm sewers, and eroded channels. The majority of this water is now treated as a problem rather than a resource. It flashes through a community creating problems of erosion and pollutant loads. Meanwhile, the perennial streams are now underground, concentrated in sanitary sewers. Our urban “streams” now flow to centralized or to onsite treatment systems. These systems were originally built around the “pollution-dilution-solution” paradigm. At the same time the pressures on the water supply have made the term “wastewater” an oxymoron.

Sustainable moisture management creates systems with certain characteristics. These systems are expected to run at or near equilibrium hydrologically over extended periods of time. They should be able to cope with a range of climactic variations. Operation, Maintenance, and Energy costs should be at acceptably low levels. Finally sustainable systems should be affordable to the majority of potential users in any given area. Economic justice relates to moisture sharing with all species and is a key to sustainability.

Content © 2007 Earthwrights