Adaptation - learnt from nature - Charleston Crossing

This post is a brief description on how vegetation show their natural adaptation with respect to water resources. On a short tour to Walnut Gulch and San Pedro (same as in earlier post), we stopped by Charleston Crossing. We walked beside the river for some time and took a good observation about the area. It was a small channel with different plants along its either sides. An interesting thing was that there were three plants primarily present in special strata (Photo-1, Photo-2).

Photo-1: Water Channel


Photo-2: Small trees in first line is willow
followed by larger cotton trees and mesquite at the back

First layer of species beside the water channel was Willow trees. Then came the cotton trees and then the Mesquite. It was not an artificial plantation.

Photo-3: Willow trees understorey to cotton trees

Photo-4: Mesquite trees lie farthest to water channel

Willow tree needs much more water and it does not have a long root to get water from higher depth so it was found nearer to the channel. Cotton tree requires less wet habitat compared to willow so was found farther from water channel.

Mesquite is adaptable to drier areas so it is found much farther from the water body. This adaptation of mesquite can also be justified with response to its root system. We could see that mesquite had a long tap root and many lateral roots. The lateral roots help plant to spread on the ground surface.

Photo-5: Mesquite Roots

On absence of water, willow trees are the first to dry up followed by cotton trees. Mesquite is the last to dry which is supported by the long tap roots that go deep into the soil and fulfill water need for the plant.

It is just a normal behavior of plants which we can see commonly in nature but it is interesting to highlight here that these natural adaptations are affected by presence of natural resources, here it is water body.

Measuring hyro & metereo parameters - Walnut Gulch

It was an early morning on October 27th, 2009 that I joined a small tour to Walnut Gulch and San Pedro with David C. Goodrich (Research Hydraulic Engineer, USDA-ARS) and Stephen Miller (student, UOA). Walnut Gulch is an experimental watershed at Tombstone, Arizona. It is taken as an outdoor laboratory for the Southwest Watershed Research Center (SWRC) program of USDA-ARS (United States Department of Agriculture - Agriculture Research Services).

Our trip started at 6 am in the morning. In around 1.5 hrs we reached the field office of USDA at Walnut Gulch experimental watershed. We were first given few introductory information about the different works done by USDA at the site.

Photo-1: Walnut Gulch - a glance

Photo-2: Activities at Walnut Gulch

Then Dave described us about how different hydrological and meteorological parameters were being measured regularly. An interesting thing to be noticed was how analogical methods of measurement were being substituted by digital measures with time. As in Photo-3, the cylindrical rain gauge is supplemented by the squared metallic strip on the ground. It helps in measuring the precipitation.

Photo-3: Rain Gauge

The circular apparatus in Photo-4 measures evaporation rate. As shown in the photo, effect of wind on evaporation is also taken into account. Rate of evaporation is measured by the change in water level in the small triangulated feature inside water body.

Photo-4: Measurement of evaporation

The apparatus shown in Photo-5 measures CO2 flux. Since all these apparatus are attached to the computers, digital measure of all parameters are obtained directly and instantly.

Photo-5: Measurement of CO2 flux

After the informative introduction, we moved to Flume 6 of the Walnut Gulch where we saw how sediment flow rate is measured.

Photo-6: Flume 6

The concreted area is made for measuring actual amount of deposit collected. Sediment deposited is now being recorded using sensors indicated by yellow markings in Photo 7.

Photo-7: Way for Sediment

Initially, the metal shown in Photo-8 was used to collect sediments within the flow and measured.

Photo 8: Metal collecting Sediment

Sediment recorded by the sensors is used to measure the sedimentation rate electronically. The video below describes how the recording works directly.

It was really an informative trip. Though not much to be done by myself, it was my first field exposure in AZ. I found it fruitful and came across how some important measures of hydrological parameters are being collected from the field.

My sincere thanks to David C. Goodrich and Stephen Miller for the opportunity and wonderful company.

Dilution is Pollution's Solution - WMG

I spent my Saturday morning on 24rth October, 2009 volunteering for the Watershed Management Group (WMG). WMG had organized an workshop at the 1325 East 8th Street.

WMG was interested in Tucson washes and watersheds. It was currently working in the Rincon Heights neighborhood to provide water quality education ad improvement. Fund for the program was provided by the Arizona Department of Environmental Quality. The major focus of the project was to reduce "non-point source" pollution - that refers to pollution from dispersed sources such as pet waste, grease, households, lawns, sediments, lawn waste etc.

The workshop was intended to empower local residents on adapting Best Management Practices (BMPs) for stormwater quality. The workshop demonstrated on installing bioretention basins, berms, curb cuts and infiltration trenches. Storm water is taken to be an important problem throughout Tucson. The Rincon Heights neighborhood is an area within Campbell at the east, Broadway at the south, Park Ave at the west and the Sixth Street at the north. The area is seen completely inundated during rainfall. So, at various spots WMG had built bioretention basins.

For the basins, we dug ditches of different sizes at 2 ft. distances from the street. Then strong rocks were used to support the wall of the ditches. Water flow towards few ditches was directed through cut curbs.

Ditches - a glance

Some have cut curbs that direct water from streets to flow into the ditch while the other types without cut curbs serve to direct water from side walks.

Ditch with cut curb

Ditch without cut curb

The cut curves are intended just to make small shallow or eddies besides the usual flow of water in streets. In eddies water moves in circular motion thus no danger of scouring as well as it facilitates water retention by the soil on either sides of the street. Care was taken that it does not turn into small channels. These cut curbs were also lined by small rocks so that it can reduce water velocity of the flowing water and thus reduce soil scouring.

Cut curb - to direct water into ditch

While in other ditches water from side walks was directed just by making the surface slopy towards the ditch. When the ditch was ready, it was filled with gravels.

Ditch being filled with gravel

Then we planted plants of different varieties native to Tucson climate. The area gets much drier during the summer and when it rains it gets fully flooded. So, plants were chosen such that they can tolerate temperature extremes of dryness as well as floods. Some of the plants used were Ironwood, Sotol, Humming Bird Trumpet, Flat Top Buckweed, Triangle Leaf Bursage, Ocotillo, Brittle Brush etc.

Dry-loving plants were planted at the upper level and plants adaptive to watery lands were planted at the lower surface in the ditch.

Ditch view after plantation - I

Ditch view after plantation - I

Compost manure was put at the base of every plant to facilitate growth. The ditch was then completely covered by mulch up to 4-6 inches to reduce evapotranspiration.

Mulch Cover

This kind of ditches/bioretention basins are made up of locally available natural resources, cheap to construct and people do not need special knowledge or skill to work for it. So, it is highly useful and in turn reduces erosion by storm water. Storm water as well as surface water when get directed to small ditches while flowing through the main street during heavy rain, it reduces water velocity and thus its strength to carry soil on its way. Besides, the storm water gets re-directed towards the ditches before reaching their respective wash. The wastes instead of getting deposited in the wash, are diluted to different areas from where they are absorbed by the ground. This facilitates retention through the soil surface and thus helps in reducing the extent of pollution as well. If the wastes end up in the washes, it would obviously increase the pollution concentration but absorption of wastes at different ground surface facilitated by the eddies has diluted the pollution.

I joined the workshop to get introduced with a group working in watershed issues. The workshop helped me learn the rainwater harvesting technique practically which we usually read in books and lectures. If there is a will, we can make our way locally and easily wihout any bigger investment. It was great fun working with them. I look forward for working with the WMG again in future !!

Activities by WMG can be accessed from here.

Friday Fun - monitoring water table - USGS

On 23rd October 2009, I joined my friend Brandon Forbes for his field work at the USGS.

The work was to get value of acceleration due to gravity (g) from different areas around the city of Tucson. Value of 'g' relative to different places in the city is used to measure water table within the study area. That day, we headed towards the east Tucson. We went to one of the sites of USGS where an artificial well was built. The well visited was numbered ' C 022A'.

Well

Well Number: C 022A

The task was to get a relative value of acceleration due to gravity using a gravitometer.

Gravitometer

This value obtained was later compared with the absolute value of 'g'. The fluctuations in the value of 'g' is used to monitor the water table in the area under study. The 'g' value here is measured in mGal (Gal referred "galileo" and is equal to 1 centimeter per second squared, source).

Reading in gravitometer

Colorado river is the major source of water for Tucson city and measuring water table in Tucson illustrates the input and extraction going on in the Colorado river. Knowing water table is also useful for locals at the work site.

However, our work on that day was not much fruitful. Due to an earthquake that had occurred 17 hours ago, earth was continuously shaking, though in very negligible extent to be felt. Because of the shake we could not get a precise value for 'g'. Data showing the earthquake can be viewed from here.

Though being interrupted by an earthquake, I had an informative exposure towards how acceleration due to gravity can be used to measure water table of an area and how it is actually being carried out in the field. A similar work like this by USGS had been done before at Lancaster, Antelope Valley, California, from November 1996 through April 1997. The report can be accessed from here. Different works by USGS, Arizona Water Science Center can be accessed through their link.

I hope to join Brandon again next time and illustrate more about how it works.

My sincere thanks to
Brandon Forbes
&
USGS family !!