Conclusion

I have enjoyed my experience volunteering with different organization in Tucson. It was great to see different perspectives on water havesting techniques. I recognized many of the techniques from concepts I had learned in my Air an Water and Watershed Hydrology classes. For example, at both water harvesting sites we discussed soil types and how to build structures to minimize evaporation.
 Having just moved to Tucson, working on water harvesting projects was a great way for me to further understand the complexities of obtaining water in a desert. It helped me to undertand that during the monsoons, it rains so much at once that it is impossible to capture much water before it evaporates. Because most the soil are so compacted, very little water is able to infiltrate into the ground. Working at the water harvesting projects also allowed me to see how much effort it takes to grow trees and other plants in this environment. The plants were placed very carefully, according to how much water they needed and what the root structure was like.
I also really enjoyed my experience learning about stream restoration. This workshop seemed to relate the most to everything we had been studying in Air and Water, as we discussed stream velocity, discharge, erosion and stream power. In class we had become familiar with the equations used to quantify streams, however it was great to see how these equations could be applied in the field. This workshop allowed me to see how streams of different velocity will erode their channels. Having the background from Air and Water gave me a better understanding of the physics behind the stuctures that we built and how they would help to return a stream to its natural condition.

The Art of Rock Work

I went back to work with Sonya at the community water harvesting project. We still had some areas to line with rock and then she wanted to fill the entire channel with mulch to decrease the evaporation. The rock work was very important in this project. Because the channel was on public land, Sonya wanted the rocks to be completely stable so the sides of the channel would not collapse should someone step on them. We did not line the bottom of the channel with rocks, but rather built up the sides with layers of rocks that were carefully placed under Sonya's guidance.



The first layer of rocks, packed tightly with dirt.



The rocks were placed in a way that resembed a retaining wall. We packed dirt around the rocks to fill any voids. In low spots in the channel we placed smaller rocks.

We also filled the channel with mulch. The mulch will help to hold the moisture into the ground and slow the evaportion rates.

The channel before we filled it with mulch.

The channel after it has been mulched. The channel leads up to the curb where the curb cut will be to drain runoff from the street.

Water Harvesting: A Community Project

To gain another perspective of water harvesitng opportunities in Tucson, I found a volunteer opportunity through the Desert Museum. A few people from the Desert Museum were involved in a water harvesting project in a neighborhood in Tucson. They had identified different areas on the street where water tended to pool during storms and decided to build channels along the curb that they could drain the runoff into. They would do this by cutting out a section of the curb to allow the water from the street to flow into the channel. This would allow the water to infiltrate into the ground as well as provide water for plants along the channel. I thought this was a brilliant idea as it seemed fairly simple and would benefit the neighborhood as well as get the water off the streets.



Water harvesting channel to hold runoff from the road.

 I liked how this project was a community effort and located along the road rather than in someone's yard. There were many peopel walking and riding their bikes by who stopped to ask what we were doing. It seemed to be a great way to educate people in the neighborhood about water harvesting. The people involved in this project were also involved with an effort to establish bike lanes and plant trees in their community. There had been other water harvesting projects in the neighborhood as well.

Sonya, explaing to people passing by what we are doing.

The plan for this project was to dig a trench along the curb and line it with rocks. The land between the houses and the channel was graded gently to allow for the water to drain into the channel. Digging out the channel took the most effort because the soil was very compacted, but by the end it was about a 12-18 inches deep. Just as we had done at Leslie's house, we built shelves that stuck out into the channel for plants to grow on.





A shelf for plants to grow

Stream Restoration Workshop Part 3

The next day at the workshop, we went into the field at Las Cienegas Conservation Area to restore streams that were downcutting through the fields. This area used to be used for catttle grazing. Our first project was to create a zuni bowl at the headcut of a stream. We dug out the area of the bowl, then lined it with fabric. The fabric collects fine sediments that are needed for vegetation to grow. We placed a couple layers of rocks down, with the largest rocks at the bottom. We also built up the sides of the bowl with rock so they did not collapse. With so many people, we were able to build the structures fairly quickly. The structures and materials are simple and the techniques can be easily transferred to other places.

Zuni bowl with a one rock dam below it

After the zuni bowl was completed, we built a one rock dam blow it. The dam is only one rock high, and should be about 1/3 the height of bank flow. While the zuni bowl helps to slow down the water from the head cut, it also raises the level of the stream bed creating a steeper slope downstream. This may cause the velcoity of the water to increase leading to more erosiosn. The one rock dam raises the level of the bed downstream to slow the flow down. When water flows, sediment will pack around the rocks.


Finishing the Zuni bowl.





Building a zuni bowl



Stream Restoration Workshop Part 2

Bill Zeedyk continued our restoration workshop outside, where we walked along a narrow channel and discussed how what we might do to restore it. It was an interesting exercise in scale, as the channel itself was no more than a couple feet wide. However, it allowed us to evaluate the channel as though it were a long channel.

At the Las Cienegas Conservation Area, one of the largest causes of erosion is road construction. If the roads are not graded properly, all the water will runoff in the same place, creating erosion and cutting down alongside the road. We witnessed many places where the runoff from the road was causing deep gullies.

Bill taught us how to evaluate the conditions of a stream by measuring the sinuosity and the entrenchment. By looking at streams on such a small scale, we were able to measure the distance between the meanders as well as the length of the meanders. He showed us examples of where baffles could be used to create meanders, as well as examples of places where the meanders were to long, which could lead to the stream cutting off the entire meander and losing its sinuosity.  This workshop gave us experience recognizing bank flow and measuring the characteristics of streams.

Gully caused by runoff from the road.

Stream Restoration Workshop Part 1

I attended a workshop titled "Erosion Control and Arroyo Restoration" taught by Bill Zeedyk. It was held at Empire Ranch in the Cienega Creek Watershed. It was a two day workshop and we started out the morning with power point lecture by Bill as he discussed the basic concepts behind his theory of "Induced Meandering."

Induced meandering is one method of restoring streams that uses structures to direct the water to reshape the channel and restore the natural sinuosity. By putting structures into a straightened channel, the water is forced to slow down and meander around structures. Bill Zeedyk's motto is to "let the water do the work." He places structures along a stream, but ultimately it is the stream that carves out its new meandering pattern. This process can take many years, depending on weather conditions and stream flows. Bill explained that the natural tendancy of streams is to take on a meandering pattern, and he is simply speeding up the process.
Slowing down the water causes sediment to accumulate on point bars and helps to sort sediment by size class.
When streams are loose the sinuoisty and increase their velocity, sediment particles are more easily transported by the flow. This deprives upstream areas of fine sediment. By slowing down the flow and establishing flood plains, streams will drop the larger cobbles first along the stream, then finer sediments will accumulate on floodplains as the velocity slows down. It is important for streams to have the layers of sediment that range from larger cobbles at the bottom to finer grains near the surface and on the floodplains. Finer sediments are more conducive for growing vegetation, while the large grains allow for infiltration and retain water.  A slower moving stream allows for the stratification of sediment. Bill emphasized the importance of stratified sediment for healthy vegetation.

Bill finished up his power point by introducing us to the various structures that he uses. Baffles are structures that are shaped like a right triangle, with the hypotenuse of the triangle along the bank, and the the 90 degree angle pointing out into the stream. This structure forces the water to meander around it, slowing down the water and creating a more sinous channel. The baffle itself should emulate the natural slope of a point bar and allow for the deposition of sediment, so that the strucutre can eventually become part of the stream.

One layer rock dams are used to create artificials ripples in the stream. They are usually 1/3 the height of the bankflow and located halfway down the meander. During low flow, sediment is able to accumulate between rocks to solidify the structure.

Zuni bowls are used to slow down water and reverse the downcutting of a channel. They are constructed out of rocks and shaped like small pools. When there is are headcuts in a stream, placing a series of Zuni bowls will slow down the flow and reduce the erosion.

What I liked about Bill's method was that the stuctures he builds are made from natural materials found around the site. They structures then become part of the stream as sediment builds up around them and eventually you would not know they were ever there. I also liked his idea of letting the stream do the work. Rather than redesigning the entire channel, he places structures in key places and allows the stream to redefine its channel.

Water Harvesting

I volunteered with the Watershed Management Group where I helped build a water havesting system in the backyard of Leslie's house. Leslie is a certified rainwater harvester and had drawn out plans to divert runoff from her front and backyards into two holding tanks. She explained that water tended to run off the sidewalk and pool in her front yard. She also had runoff from the roof that would pool near the house. The soil at her house is primarily compacted clay and there is very little infiltration. Her goal was to divert the water into two holding basins in the backyard using culverts and a rock-lined channel.
 We began by digging two holding tanks, which were connected by a narrow channel.We used larger rocks to stabilize the sides of the channel and placed small rocks in the bottom to minimize erosion. Her front yard was graded to a slope of 2%, which then drained into a culvert. The culvert would divert all water collected in the front yard to a channel that ran along the fence in her backyard and into the first holding basin. Once the first holding basin fills up, the water will run through another rocklined channel into the the second holding basin. We planted various plants along the sides of the channel and basins. By building a shelf for the plant, the plant sits above the water while still allowing the roots to reach the water level.

  Leslie in the first basin explaining to a volunteer how to build shelf for the native plants

   

     Lining the channel with rocks.


    A completed catchment basin.



 
 A completed basin with a channel allowing flow into and out of the basin.