runoff into some body of surface water
evaporate or
be captured directly (ei rainwater harvesting)
Most of our discussion focused on the factors that determine whether water will infiltrate or runoff - you should be able to explain how each of the following affects this balance:
hydraulic conductivity (a function of water saturation of the subsurface and permeability)
characteristics of the regolith (grain size, grain size distribution aka sorting, level of flocculation of clays)
presence of hydrophobic soils
slope
vegetation
water temperature (viscosity)
An extreme example runoff dominating over infiltration occurs in urban areas where the infiltration of rainfall is drastically reduced due to the prevalence of impermeable surfaces such as roads, buildings, and parking infrastructure. Burlington, VT has recently adopted a tax structure that addresses the burden that owners of large impermeable areas place on the local sewer facilities by charging businesses per area. We addressed why it is a good idea minimize urban runoff in any community and why it is especially important in municipalities with CSS systems. We also discussed how common these CSO are in the USA.
Following today's discussion, you should be able to define/explain the following concepts: porosity, connectivity, permeability, sorting (well sorted, poorly sorted), sand, silt, clay, viscosity, impermeable, CSS (combined sewage system), CSO (combined sewage overflow).
Material relevant to our lecture today can be found in the first half of chapter 5 of Applied Principles of Hydrology and in readings assigned here. Material on NYC's CSO situation can be found here.
For Friday, please read (and come ready to discuss and/or be quizzed on) the following:
Catching rain water is against the law By John Hollenhorst - about Utah's rainwater harvesting law
Who owns Colorado's rainwater? by Nicholas Riccardi - LA Times article written just before Colorado's law was changed
It’s Now Legal to Catch a Raindrop in Colorado by Kirk Johnson - NY Times article written just after Colorado's law was changed
PowerPoint slides shown in lecture today are now available as a .pdf on Sakai.
The my maps page has been updated with the locations mentioned in today's lecture.
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