Sunday, August 25, 2013

Beggars Can't Be Choosers: Every Drop of Water Counts

In the perpetual conflict between human water use and allowing natural watersheds to function we face a dilemma. Some of the best, and most consistent areas for year round water flow in riparian habits are inherently human modified systems.

Calleugas Creek. Camarillo CA
Above is a pic of Calleugas Creek taking by yours truly in late August. As you can see there is abundant riparian vegetation, including known beaver fodder such as willow and various reeds, and year round flow. Much of the year round flow in the Calleugas watershed is due to human discharge from agriculture, waste water discharge, water reclamation, and urban runoff. All of these contributing factors makes Calleugas one of the more notoriously polluted systems in California- but all of the fertilizer runoff stimulates a riot of plant growth (native and non-native btw). Despite the less than ideal water quality a mature steelhead female was recently found in the Conejo Creek tributary not too far from where this pic was taken. Being a federally endangered species this deceased fish is causing all kinds of havoc with local housing/construction projects. Make sure to read the link I provided above but the crux of the controversy is this; Conejo creek, which would naturally run dry, is fed by discharge through several municipal water treatment discharge facilities. In effect this discharge is creating a water flow regime that, some argue, would not normally even exist there. Steelhead, noted for their maverick tendencies to explore and colonize non-natal streams, may be coming up this watershed due explicitly to the anthropogenic year round flows. Should the municipalities/construction firms/treatment plants be obligated to maintain these flows for the fish in light of this?

Well, you can probably guess where my bias lies, but let me just suggest that given the amount of water  hijacked from the land over the years through human use- we do owe it to the land to optimize the feasibility of even heavily human modified water inputs for wildlife use. In arid lands, every bit of water, even potentially polluted/modified systems can provide habitat as the shown above by the steelhead in Conejo Creek.

It should be noted here that beaver with their ability to dam and slow down the flow of water, could significantly 'cleanse' such systems and optimize them for rehab. The large pools they create further enhance the area for vegetation to get a foothold and then the vegetation filters the water of pollutants. Polluted sediment also settles in these pools for bacterial cleansing.

Let's look at some of the other anthropogenic spots for riparian rehab I have came across.

Ventura Wastewater Settling Pools
Above are some pics of Ventura City wastewater settling pools, which slowly discharge into the Santa Clara River estuary. They are famous for bird-watching, attracting numerous waterfowl and even occasionally swans. The public is allowed to explore these ponds and as you can see there is abundant willow thickets. I've often thought that these ponds would be an ideal spot to place beaver. In these ponds they would not form dams, but it is an enclosed area with abundant beaver food where you could  raise beaver and then place into other watershed from here. Some of the waterfowl found here below.

Another hot spot for riparian rehabitation in human modified habitats is under freeway overpasses. In the Conejo steelhead story I mentioned earlier you will notice that the fish was found under the famed 101 freeway. Now, freeway overpasses don't immediately spring to mind when you think about potential spots for riparian wildlife refugia but they do provide some benefit in my experience. The shade they create cools the water down, a noted benefit for steelhead and other fish. And this shade, coupled with freeway pilings often allows water to linger longer though out the year in this microhabits.  In short there is a strong argument to be made that freeway overpasses may actually serve as important refugia for aquatic species through the dry periods. Below are some pics I took back in April in the Santa Clara river underneath the 101 freeway. It should be noted that we had a really bad year for rain and the main body of the river was unusually dry by April in this stretch of the Santa Clara.

In water strapped socal, beggars can't be choosers when it comes to water availability and riparian habitat. A creative use of human modified systems, coupled with beaver reintroduction in a pragmatic and realistic method, offers our best bet for enhancing the riparian habitats we have left.

And here is one of the best videos I have seen yet on beaver reintroduction into an arid river systems, the San Pedro of southeastern Arizona. Go read the blog post form Earth's Internet where I first found the video, a friend of this blog, where there is an interesting post up about beavers, Colorado River, and the unique and almost extinct native fish fauna of the Colorado River basin:

How Human Dams Destabilize River Food Webs and Beaver Dams Stabilize Them 

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Wednesday, August 14, 2013

Anatomy of a Drying River

I have, on more than one occasion, been met with a little derision by people from more wetter parts of the country when I discuss southern Californian rivers. What constitutes a "river" here may for most of the year be little more than a stream or actually completely dry up. Never the less in certain water starved parts a very generous definition of river suffices. This ephemeral nature of many of our rivers has much to do with human use such as wells, diversions, and dams. But anyone who goes out and hikes into our watersheds should be familiar with creeks that show good flow but then disappear into the earth and then often times reappear later on downstream. As a child I was always puzzled by this; where did the water go? And then, with no obvious signs of surface input, why did the water sometimes reappear downstream?

It was not until I understood the three dimensional nature of water movement in our landscape that I came to understand this pattern better for what it is. Our streams and rivers, ephemeral as they may be, offer a view into water dynamics that those from wetter parts never fully get to realize.

The first useful concept to visualize is groundwater. Groundwater is a zone of saturation that lies underneath in the earth at varying depths but more or less follows the contours of the land. Wells tap into this. Ponds, rivers, lakes, marshes and other bodies of water represent the interface between the water table and the surface.

USGS (c)
Seen three dimensionally it can be seen here how, even with no obvious signs of surface recharge,  a stream can flow all year long with adequate recharge from groundwater. Such a a stream would be characterized as a "gaining" river. In our ephemeral streams this would represent the reappearance of water after a dry part or a river that flows year round. 

But what is also crucial to dynamic watersheds is an understanding of aquifers. Aquifers are large subterranean bodies of water, often confined by certain layers of impervious sedimentary rocks. Many arid regions depend on withdrawing from aquifers for irrigation purposes. When these aquifers become depleted of water they want to suck it back up, either from the water table/rivers or even from the ocean (saltwater intrusion). When the aquifer is hungry it will lower the water table and deplete above ground water resources. You now have a "losing" stream and this is where rivers/streams dry up.

USGS (c)

Seen in this manner you can visualize the above ground portion of the water table- streams, rivers, lakes etc. etc- as representing a dynamic equilibrium between above and below ground water flow. Where underground aquifers are happy, above ground flow is good and the water table is high. Where aquifers are thirsty the water table is low and above ground flow is minimal.

And at this point in our discussion, if you have been connecting the dots, it should start to crystallize in your skulls how beaver- with their ability to store water in dams and recharge aquifers slowly through the year- can transform a "losing" stream system into a "gaining" one. And this ability of beavers to create a "well watered land" is especially pivotal in arid regions.

Immature Black-Crowned Night Heron. Oxnard CA Steve Nash (c)