Santoyo & Associates
santoyo at earthflow.com
Sun Jun 3 17:00:26 EDT 2001
Claude, (Vint, Toby, et al),
Vint and Toby have had excellent points for you. Remember too that
swales and water catchments are only one half of a calculated
response to (specific) landscape dynamics. Plants (trees, perennials
and annuals) make up the other half of the equation -"converting
infiltration to biomass" is the sound bite.
The usual argument against water catchment is about depriving surface
streams of overland flow. The response to that argument is that;
although swales and other catchments do reduce overland flow -the
best and most significant thing that infiltration does is to increase
"baseflow" of surface waters through groundwater recharge (as opposed
to surface runoff) -baseflow is much better quality of water and
contributes over a significantly longer duration.
As with all techniques and technologies it is in fact only
appropriate if it is truly filling a need (solving an issue ie;
aforestation and reforestation, reduce flooding problems, etc...)
You wouldn't want to infiltrate more than the soil could safely hold.
Maybe a better question is when would you not want to use water catchments...
I'll tell you some mistakes I have made and have seen -You don't want
to work on too steep or too shallow of a soil profile, even in the
northeast but especially in the west, bedrock can be quite close to
the surface especially on hills...under those conditions, cutting
swales for infiltration has caused landslides, flooding and erosion -
it can all be mitigated through calculating coefficients of run-off
friction and saturation rates to determine the frequency and depth of
catchments -to be safer, novices should stick to working on less than
15 degree slopes.
One idea that I came up with (after I caused a small landslide) is,
instead of making the water soak down quickly into the soil, make it
soak up! ..as in wick up into a row of compost or straw bales on
contour end to end, allowing a slower release. This technique has
proved successful in both a "woods-cultivated" ginseng crop that I
installed in upstate New York and a hillside olive grove in coastal
In addition to WATER FOR EVERY FARM, check out PRINCIPLES AND
PRACTICES OF GRADING, DRAINAGE AND ROAD ALIGNMENT: AN ECOLOGIC
APPROACH by Richard K. Untermann (available from the bookstore at
San Luis Obispo, California
santoyo at earthflow.com
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