Science with Phil: Episode 2

July 20, 2010 by Parks Conservancy Staff

Yesterday's post showed you an example of how our Management and Maintenance team constructs a soil profile for highly-trafficked areas in the parks. Part of the advantage of this kind of soil structure is that it helps to infiltrate water more effectively than some of the existing soil structures in the parks. And better water infiltration leads to reductions in things like erosion, water runoff, and water that reaches the city's combined sewer system. Plus, the deeper the water is able to infiltrate, the more groundwater recharge will take place.

Today we'll watch over the course of an hour as we simulate a five-inch rainstorm in the test tube. We'll see how quickly the water reaches the drainage gravel after entering a system of completely dry soil.

Five inches of rain in ten seconds--that's a pretty big storm!

[youtube=http://www.youtube.com/watch?v=ZW-qD864EZw]

Checking in after 4 minutes:

[youtube=http://www.youtube.com/watch?v=MWRwm2sJrX0]

What do all those air bubbles mean?

[youtube=http://www.youtube.com/watch?v=nHONaZTv3wo]

25 minutes later, the water begins to hit the bridging gravel - will the sandy soil on top start to drain into the gravel too?

[youtube=http://www.youtube.com/watch?v=Xg0cxDzlcZQ]

35 minutes later, the water is making its way fully through the system:

[youtube=http://www.youtube.com/watch?v=FIDIjaS8A9k]

An hour later, water begins to leave the system. How much water will remain in the root zone mix to feed the (hypothetical) plants?

[youtube=http://www.youtube.com/watch?v=2Dc966ryFTA]

Tomorrow we'll add even more water and compare the rate of water infiltration into dry soil to how fast it infiltrates to already-moist soil. Any guesses which will go faster?

Parks Management, Stormwater and Green Infrastructure