Rain, runoff and surprising ocean springs
October 19, 2010 § 3 Comments
Rain brings runoff to mind. Our concreted river systems shunt large volumes of fresh water to the Pacific Ocean very quickly; historically, the process occurred much more slowly, with infiltration occurring throughout our watersheds, moving subsurface flows of water out to the sea, particularly San Pedro Bay/Alamitos Bay. This groundwater movement created pressurized aquifers – giving rise to places like Artesia.
Consider the following historical anecdotes, from James Reagan’s oral histories taken in 1914:
When General Bouton put down his deep wells the pressure was enough to raise the water fifty feet into the air. On one occasion a well driller had his tools shot out of the well with considerable force… -C.W. Caseboom
Bouton Lake in Lakewood was created by overflow from one of these wells.
The oral histories also tell us of freshwater mixing in the ocean. Back to C.W. Caseboom:
Captain Polhoumas of San Pedro has told me that a ship could take on its supply of fresh water out in the ocean off Alamitos Bay. There was an immense volume of fresh water that emptied into the ocean at that section opposite the Alamitos region. People bathing in the sea at one of these places upon going to the other would at once notice the great difference.
General Bouton’s descriptions suggests that these could have been almost like springs in the sea:
It has been the practice of the fishermen at San Pedro when they arrived at about one mile outside of the beach, and about midway between Long Beach and San Pedro, to lower a jug weighted so it would sinkand corked up so that when it reached a certain depth the pressure would push the cork in, and the jug would fill with pure, fresh water.
There is another place at Redondo where a great supply of fresh water empties into the ocean from the floor or bed of the ocean. There is a great hole in the bluffs in the cliffs near Redondo, where no doubt, fresh water came in from some subterranean waterway.
C.H. Thornburg adds:
In the early days John McGarvin and many others have told me of being able to see the fresh water boil up in the salt water about … of a mile from the shore outside from Alamitos Bay. It was no trouble to distinguish the color of the fresh water from that of the salt water and for that matter, get a supply if necessary…
(At moments like this I wish I were a marine ecologist, to speculate on the likely effect of this mixing on the distribution and diversity of marine life just off our shores)
Many of the old-timers interviewed believed there was no relationship between surface flows in our rivers and their wells. They refer to clay strata for example, that would block migration of surface waters to groundwater. However, our watersheds have diverse soil profiles – for example, the San Fernando Valley is highly pervious. Rain could easily infiltrate to greater depths there than, for example, in more clay-rich Ballona Creek lowlands.
In the short period of less than a century angelenos managed to pump down these plentiful aquifers to the extent that seawater intrusion – the subsurface movement of saltwater into coastal freshwater aquifers – became a serious problem. Today injection wells pump water into these aquifers to hold saltwater at bay. And rainfall – our free resource – isn’t able to plump the aquifers as effectively as it could in LA’s pre-pavement, pre-channelization existence.
Here’s a drop in the bucket contribution you can make: if you own a home or other property, revamp your landscape so it can receive and infiltrate your runoff (aka create a rain garden!). Clay soils? Perhaps a subsurface trench with gravel fill can hold rainwater and allow it to seep into the ground at that slower rate your soil may require.
Creek Freak has covered organizations and examples that you can draw from for inspiration, here’s a few:
The Ocean-Friendly Garden workshops taking place around town are also a valuable resource for you.