The overall goal of the following procedures is to design and construct simulated urban lawns to measure total runoff volumes and to simultaneously collect runoff water subsamples. The runoff water from simulated urban lawns will be measured and quantified for chemical constituents. This is achieved by selecting a site with a uniform three to 4%slope and an adequate plot area for location of the facility.
The second step is to construct a retaining wall at the bottom of the plot areas, which includes runoff, collection troughs, and will allow the collection of all runoff from each plot and delivery of it to the measuring and sampling equipment. Next, the measuring and sampling equipment is installed below the retaining wall in order to accurately measure the amount of runoff in discrete time intervals, as well as to collect runoff water samples for analysis. The fourth step involves the final preparation of the plot areas, including installation of individual plot irrigation, plastic barriers between plots, small above ground berms, and a diversion ditch above the plots.
Finally, the plots are planted with St.Augustine grass sod. The irrigation system is activated to initiate a runoff event and the resultant water samples are collected and analyzed for chemical composition. The main two advantages of our facility over those in Florida, Pennsylvania, and Ohio is that our facility is constructed on native undisturbed soil and also the plots are such that they include natural variability and microclimate effects.
Research U using this facility will focus on key environmental issues such as nutrient runoff from lawns and landscapes in urban settings that will also help us develop and utilize, implement key best management practices to minimize or even prevent nutrient losses from urban lawns and landscapes. Although research using the facility currently can provide insight into nutrient losses from St.Augustine grass lawns, it potentially could be used for other grasses and products such as soil amendments, herbicides, and pesticides. Generally speaking, individuals wishing to replicate this facility will initially struggle with the site location and then with the design and construction of the retaining wall.
Visual demonstration of this site is critical in order to give people an example of the large amount of water that can come off of landscaped areas when they're irrigated at rates higher than what the soil can absorb. To begin, locate an area of undisturbed soil with a uniform three to 4%slope and conduct a topographic survey on the area. Next, delineate a 10 meter by 100 meter area with an average 3.7%slope, and divide the area into three 10 meter by 33.3 meter blocks.
Then subdivide each block into eight 4.1 meter wide by 8.2 meter long field plots To initiate construction. Pour 4, 000 pound test ready, mix concrete into the previously prepared forms and use vibration to remove voids when the forms are full. Trowel the upper surface to create a smooth finish with rounded edges and remove the temporary plastic covers on the drains to enable final surface preparation.
Next, ensure that the finished concrete surface is level with the soil surface at the bottom of the plot, and that it has a 1.27 centimeter slope to the drain to allow unimpeded water flow from the soil to the drain. Then form reinforced steel concrete pads 1.2 meters wide, 1.8 meters long and 15 centimeters thick below each drain outflow with a 0.5%slope away from the wall, ensure that the top of the pad is 30 centimeters below the bottom of the drain outlet. Provide a weatherproof electrical outlet on the side of the retaining wall above each pad.
To prepare for instrumentation, cut discharge pipes flush with the concrete wall. Install a 1.2 meter long H flume immediately below the drain outflow and anchor the flume on the wall level from side to side with concrete anchors and screws. Next, support the front of the flume with an adjustable stainless steel stand and use the adjustments to level the unit.
Seal the joints between the flumes and the concrete with tub and tile sealant. Install a flow meter on each pad and minimize the length of tubing needed. Then install a portable sampler on each pad and minimize the needed of tubing to reach the sampling tube.
Next, install previously fabricated stainless steel covers over the wall and the flumes to prevent the precipitation from entering the trench drains and flumes fill and tamp any minor voids on the up slope side of the wall. Using native topsoil from adjacent field areas, use a small walk behind trencher to cut a 10 centimeter wide 30 centimeter deep trench on the remaining three sides of all plots. Next, insert 40 centimeter wide strips of 0.10 millimeter thick, clear plastic vertically in the trenches to prevent lateral movement of water between plots.
Then install irrigation pipe and six irrigation heads on 4.1 meter square spacing for each plot, backfill and lightly tamp all trenches by hand and mount the soil into a five centimeter tall by 30 centimeter wide berm over the trench area to prevent lateral movement of surface water between plots. Next, adjust irrigation heads to the top of the soil height in the berm areas, construct a diversion ditch to prevent up slope water from getting on the plots. Use a box blade to cut a V-shaped channel approximately 20 centimeters deep in the center and two meters across so that the center of the channel is 1.25 meters above the high side of the plot area and extends across the upper side of all plots.
Cut a sloped trench in the 30 centimeters below the channel bottom with a minimum slope of 0.5%going to the end of each block to ensure good drainage smooth trench bottoms by hand and survey them to ensure a uniform slope. Then add five centimeters of washed six to nine millimeter P gravel to the bottom of the trenches. Place a 15 centimeter diameter slotted drain line on the gravel surface and fill the trench with more gravel.
Next, cut trenches at the ends and between the blocks of plots to root drainage water to discharge locations below the retaining wall. Place a 15 centimeter diameter plain corrugated drain line in the trenches and backfill with the excavated soil. Cover the trench and channel area with a layer of large five to 15 centimeter diameter bull rock to for a runoff event.
Take initial readings of water meters and measure the soil moisture content of all plots. Next, remove the lids from the valve boxes located at the head of each plot and record the initial water meter reading for each of the 24 plots using a portable handheld moisture probe, measure and record the soil moisture content of each plot program flow meters and samplers to measure, flow and collect samples as desired. Operate the irrigation system for a predetermined time to apply sufficient water to cause runoff.
Record the ending water meter readings for each of the 24 plots. Then collect irrigation water samples from the spray heads during operation. Data from the flow meters can be viewed in tabular or graphical forms and provides an accurate measurement of the volume of water lost as runoff from the plot area.
Measure the electrical conductivity and pH of the water samples by dipping probes directly into subsamples of the water placed in clean beakers. Then filter additional 50 milliliter subsamples of each collected water sample through a 0.7 micron glass microfiber filter. To prepare for chemical analysis, 24 plots were analyzed and yielded topsoil depths ranging from a low of 25.0 centimeters to a high of 51.5 centimeters.
The slopes ranged from a low of 3.2%to a high of 4.1%Runoff events were performed on two separate days. Prior to sodding, the plots had been well irrigated to ensure optimal performance and measurement. The runoff volumes from the first trial had a mean of 213.5 liters and a coefficient of variability or CV of 38.2%In contrast, the soil was much drier prior to the second runoff event, which resulted in a lower average runoff volume and cv.
In this case, much of the applied water infiltrated into the soil beneath facade. The pH values for all 49 water samples collected after the first runoff event the morning of August 9th, 2012. After laying sod the previous day averaged 8.4 standard units with a minimum of 8.1 and a of 8.9 units, resulting in a very low CV of 1.5%Proper operation of our facility coupled with accurate chemical analysis of samples will give us very important information on the sources and fates of nutrients in urban ecosystems.
When conducting research experiments using this facility, it is important to carefully design the research protocol in advance so that the resulting data will be valid. Because this facility was constructed on undisturbed soil, the data includes variability that's typical of natural soils. So using this facility, we can investigate water quality coming off of a number of grasses and using a variety of products such as soil amendments, pesticides, and herbicides.
After watching this video, you should be able to design and construct a large field scale facility with replicated plots that will allow simultaneous collection of water volumes as well as subsamples for quantification of various water parameters such as nutrients and perhaps pesticides. Construction of a facility of this magnitude requires the use of large amounts of heavy equipment such as tractors, loaders, backhoes, trenchers. It's essential that you have properly trained equipment operators and a good safety plan to protect all the workers and avoid injury at the work site.
