So I'm looking for some good resources (permie-related a plus) on soil hydrology.
Here's the issue. I recently watched one of Ben Falk's presentations on YouTube where he mentioned that his homestead site was able to hold 4 out of 6 inches of rain received in a single event. Coming from an area where the little salmon habitat that remains relies on sufficient runoff to keep streams up, I gasped. If the land holds most of the water, then people and animals downslope and downstream suffer the consequences.
I later learned that the problem is my lack of knowledge and flawed perceptions.. so, I want to learn how hydrology really works, what happens to water as it sinks in the soil, and how streams/rivers are fed by water we don't see.
I'm very interested in this too, I actually was about ready to start my own thread, but B.E beat me too it! I have a couple specific questions about water/soil interactions if the OP is alright with me jumping on this thread - otherwise, second on the want for some good resources.
It's just physics, guys. Nothing more difficult than the mechanics of fluid flow through a porous structure. You read the stuff, look up the words you don't know, get comfortable with the concepts and start using them. See how the principles are at work in the world around you as you go about your daily business.
Here is a good place to start, a primer of how rainfall moves through the landscape in British Columbia. Study it over and if you have questions, ask away.
This is a lot easier than chemical engineering where you have counter-current flows and the possibility of different phases. Here, everything moves downhill (force of gravity) and you only have one liquid phase. If you have two liquid phases, somebody did an OOPS! and a pipeline broke.
Edit to add: This old reference, somewhat dated, but it does have nice conceptual drawings.
So if you get 7inch of rain on Sunday and the soil did not hold any, the salmon river would flow with all that water in 1 day and come monday, the river would be dry.
It would also be dry on Tuesday pretty much till the next rain event. And all your fish and fish eggs would die.
So what you really want is for the soil to capture and hold all 7inch of rain on Sunday and slowly release 1inch of rain every day back to the river.
In both case the river get the same 7inch of rain per week/month/year.
But it moves in such a way where we dont have 6 days of no flow/drought and 1day of flooding.
Now lets say the soil held on to that water and never released it. what would happen is that after the 3 sundays the soil would be completely full.
And any time it rained after that the rain water would have nowhere to go but down to the river, and we would be right back where we were.
Except the soil now has water to support plant, endangered animals like the hummingbird and also feed humans.
But I guess the real question would be if we are getting 7rainfall and we are using 3 to grow apples and sending 4 to the river.
Wouldn't it be better if we just killed all trees and send all 7 water to the river.
Well trees help to weather bedrock to create infiltration. and moderated water flow.
Which means the river is better off with 4inch over 7 days or 1/2 inch flow each and every day. vs no flow for 6 days and all 4 or 7 inch of rain in 1 day.
Without the trees to help infiltration, the strong flow of the floodwaters might erode away all the plants and animals that salmon needs to eat, also wash away all their eggs. possible damaging it.
Without the trees using the rainfall to humidify the air, the rivers and lakes would lose water at much higher rate due to evaporation.
And without plants releasing water into the air, the amount of rain that falls drops to really low numbers.
Most of the water that the trees pulls out of the soil ends up in the sky and it all falls back down as rain in some other river/ecosystem.
I think my first perception problem came from a lack of understanding in what happens to the water when it sinks into the ground. I figured it was absorbed and, well, effectively ceased to exist as 'water'. That it basically stays as water and 'flows' underground is news to me.
Location: Western Washington
posted 5 years ago
Can't wait to get a chance to check out the links John.
One of the specific questions I have has to do with water saturation, aggregates, and flat soil.
I dug out what I hope to get to seal as a pond and threw a bunch of really rich dark loamy clay soil up onto what is bit by bit becoming my second suntrap hugelbed. The topsoil is some of the best on my property having been completely engulfed by a rambling rose for decades. The soil is almost black it is so richly brown - the subsoil is a white/grey clay. Anyhow... I dug this out and have been trying to get it to seal and my ducks and geese have been using it when full but it always drains. So I've left with this flat pudding on the bottom. I potted some up for shits and giggles and much to my surprise as it dried it began to re-clump and form stable aggregates again. Not quite as nice and fluffy - definitely more dense but still not the impenetrable brick I was thinking I was going to get. So I'm wondering about saturation and flat soils. Which is a function of water and soils ability to retain it and I guess in this case the magic of humus. Jeez - I feel like I'm getting off topic already
Freakin' hippies and Squares, since 1986
posted 5 years ago
Landon, I'm inclined to think that your problem of the clay not sealing is a chemistry problem, not a hydrology problem. There are many types of clays, and the chemistry of the clay molecules gives rise to its macroscopic porosity -- if you have sheets of clay molecules that freely let water pass between the sheets, then you are going to a hard time getting the clay to "seal up". On the other hand, if you have a clay that has a large amount of montmorillonite in it, the sheets swell up when they get wet and the water has a difficult time passing along the sheet. And even among montmorillonites, it makes a difference what the cation is. Montmorillonite that has been treated to remove the calcium and potassium and iron and replace them with sodium will swell up much more and hence make a better seal.
You may want to check with the geology department at the local university and ask them what kind of clay you are dealing with. Ask them if they have tinkered around with a chemical treatment to the local clay that will make it swell more than it already does. If you strike out with them, then maybe we have to do a little backyard chemistry and see what we can treat the clay with to change its hydrological parameters.
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