Seepage Losses from the Franklin Canal between the Heading to Ascarate Wasteway

Transcription

1 Seepage Losses from the Franklin Canal between the Heading to Ascarate Wasteway Prepared by Delia Comeau, UTEP Mentor: Zhuping Sheng, Ph.D., P.E, TAMU Bridges Program NIH / University of Texas at El Paso Texas A&M University Agricultural Research & Extension Center El Paso Community Collage June August 2003

2 Contents Abstract. 2 Background... 3 Method and Materials 4 Field Data...6 Seepage Losses Analysis...9 Summary and Discussion...9 Acknowledgements...10 References 10 1

3 Seepage Losses from the Franklin Canal between the Heading to Ascarate Wasteway Delia Comeau Abstract Canals deliver water for municipal and agricultural uses in the Paso Del Norte region. It has been suspected that water flowing through this man made path of least resistance has been continuously lost due not only in part to evapotranspiration, but more so in seepage. Previous studies also confirmed existence of seepage losses. To justify lining canals to increase water supply, the quantity of water being lost should be accurately determined because the lining canal is very expensive. This report presents preliminary findings in flow patterns and seepage losses along the first 5 miles of Franklin canal, which annually delivers thousands of acre-feet of water to irrigate thousands of acres of land along its way. The seepage losses were estimated by the current meter measurements of inflow and outflow. The preliminary results show that seepage losses vary greatly and range from 0.48 cfs to 1.75 cfs with an average of 1.12 cfs per mile. Additional measurements and analyses are in progress and are projected to further confirm potential for water savings by lining canals. 2

4 Background Canals deliver water for municipal and agricultural uses in the Paso Del Norte region, which includes cities of El Paso, Texas; Las Cruces, New Mexico; and Ciudad Juarez, Chihuahua, Mexico and four irrigation districts. It has been suspected that water flowing through this man made irrigation system has been continuously lost due not only in part to evapotranspiration, but more so in seepage. For example, the Franklin canal, which is 28.5 miles in length, was constructed in 1890 and the infrastructure of this canal has not changed in those many years since its creation. Previous studies confirmed existence of seepage losses (Blair 2001, Sheng and Brown, 2002). Previous reports describe experiments such as on site investigations such as ponding and discriminating between evaporation and seepage. Both field and computer data concluded to future applications, but agreed there to be a higher occurrence of leakage in unlined irrigation canals. Ponding tests (Sheng and Brown, 2002; Sheng and Wanyan, 2003) conducted by the TA&MU agricultural research and extension center indicated an average of.728 cubic feet per second per sq. ft of wetted area being depleted from the ponds with evapotranspiration already being taken into consideration. They concluded that there is a great potential for water conservation by lining canals in the Paso Del Norte region. A method for discriminating between evaporation and seepage losses from open water canals written by Bosman (1993) for the department of water affairs and forestry in Pretoria, Africa describes the importance of calculating the water losses suffered by evaporation. Explaining that these large volumes cannot be disregarded because when added to seepage losses, could have significant consequences in canal management and water distribution. Using a concept similar to that of the ponding tests, two blocked off concrete lined canal compartments having sealed and unsealed joint treatments averaged 11% monthly losses. Respectively, unsealed compartments suffered 30% and sealed losses where 1%. To justify lining canals to increase water supply, the quantity of water being lost should be accurately determined because the construction of lining canals is very 3

5 expensive. The objective of seepage loss studies presented in this report is to identify the potential water savings by lining canals. The results can help irrigation districts prioritize canal lining, optimize the design of lined canals. conservation efforts increase the water available for long-term supply in an area of extreme drought and high population, which can eventually improve the quality of life because the water is a lifeline of the communities. Methods and Materials The wading method requires not only an amount of field duties but also those in safety as currents and canal bottoms can be undeterminable at point of entry into canal or during measuring activities. It is necessary to establish a rescue plan and evaluate potential hazards, as well as, the recommended use of floatation devices. For this experiment sites were already selected falling into necessary physical categories such as having a depth less than four feet, its accessibility, and vegetation being sparse, above requirements have been met and were not included in this report. To determine the depth of the water place a staff gauge that has been previously fixed or if a bridge is available above the canal center. Allow gauge to touch bottom with the bed. To determine the width of the canal, plant a wooden stake onto one bank and attach a tag line running the line across the canal perpendicular to flow. Apply the second wooden stake to the opposing bank and attach tag line again. This line must be kept in place for the duration of the testing, as it serves as a marker for subsection intervals necessary for readings. At this point air temperature, wind velocity, and humidity are measured and recorded for estimate of evaporation. In assembling the current meter and wading rod the water level must not be higher than the main rod. Every wading rod has a top setting mechanism to allow for depth adjustment. Next connect the counter meter with the current meter using 5/32 cable. Once meter is assembled and water depth has been established a flow measuring method must be chosen. There are three types of methods to use, the one, two, and three point methods (Rantz and Others, 1982; USBR, 1997). Each of these is dependent on depth of the water 4

6 as velocity decreases with depth, due to friction between the bed and water. For depths less than 2.5 feet, the one point method is used, and the current meter must be adjusted at 60 % of the water depth from the surface and should detail about 1 % of the total mean velocity of the water. The two-point method involves measuring at two points in the depth, one at 20 % and the other at 80%. This method is used when water is more than 2.5 feet deep. The last method of measurement compensates for accumulation of sediment and/or trash adding a further point at 60 % water depth. The hydrographer must be aware not to intrude upon the natural flow and stand downstream and to the side of the wadding rod also being aware of any obstacles such as boulders or tires. Revolutions are counted using a digital meter reader each being at least 40 seconds or longer. Velocity is calculated by the following equation in cubic feet per second (cfs): V= R Where R denotes revolutions per second. Figure 1 Sketch of discharge computing method (From Nolan and Shields, 2000) 5

7 Then discharge will be calculated as shown in Figure 1. The total discharge is the sum of discharges for all subsections. The data is either recorded manually on the datasheet, or saved automatically by data logger. General equipment used included tag lines for measurement of canal width, thermometer and wind meter to later evaluate evaporation levels to be compared with weather station. Field manuals for reference and maps for locations and distance verification, as well as data sheet to record air temperature were also a part of general equipment. The wading equipment included a chest wader for safety of the person in the canal as well as a propeller current meter to measure velocity of the flowing water. This meter uses a series of small cups to record velocity; these measurements are then fed back to a computer system attached to the wading rod. The wading rod is for supporting the current meter while working in shallow and moderate depth waterways. The rod uses a base plate to rest on the bottom of the canal. Field Data Map 1 shows the sites for flow measurements and distance along the Franklin canal between sites. Table 1 shows two measurements of total flows at the heading and Ascarate Wasteway and geometry of the cross-sections to be used for unit seepage losses. Date 6/25/03 7/14/03 Location Table 1 Current Meter Flow Measurements Flow (ft^3/sec) Loss (ft^3/sec) Depth (ft) Top Width (ft) Bottom Width (ft) Slope Franklin Heading 103 Ascarate Wasteway Franklin Heading 58 Ascarate Wasteway

8 Figures 1 through 4 show water depth and velocity profiles at two sites. Velocity distribution was not uniform across the canal bottom and differed by the site and time. In general, velocity is reduced near both banks and is higher at the center. depth changes with variation of the canal bed and total flow in the canal. width(ft) Velocity(ft/s) /Depth(ft) velocity depth Figure 1 Velocity and water depth profile at Franklin Heading on 06/25 7

9 Velocity (ft/s)/depth (ft) width (ft) Velocity depth Figure 2. Velocity and depth profile at Ascarate on 06/25 width (ft) Velocity(ft/s)/ Depth (ft) canal bottom velocity Figure 3 Velocity and water depth profile at Franklin Heading on 07/14 width (ft) Velocity (ft/s)/ Depth (ft) Velocity width Figure 4. Velocity and water depth profile at Ascarate on 07/14 8

10 Seepage Losses Analysis Unit water losses from current meter flow measurements based on inflow and outflow measurement and canal cross section geometry such as width, depth, and slope were calculated in Table 1. As shown in Table 2 the unit water losses measured ranged from 0.22 to 0.9 cfs per mile or 0.48 to 1.78 per acre-feet per mile per day. An overall season loss of acre-feet per mile was calculated by multiplying the 243 day irrigation season by the average daily amount lost at the site. The total water losses for first 5 miles of the Franklin canal amounted to 1,350 ac-feet per year, which can supply approximate 400 acres of crop land or over 3,000 household for one year water supply. It should be noted that water losses measured by the current meter also include evaporation from the water surface and vegetation evapotranspiration. Seepage losses are the difference between the measured losses and estimated evapotranspiration losses. Table 2 Losses from Current Meter Measurements Unit Date Estimated Calculated Losses Estimated losses Wetted over Unit from Losses Perimeter Wetted Losses Table 1 (ac-ft (ft) Area (cfs/mile) (ft^3 /sec) /mile/day) (ft^3/sq ft/day) 6/25/ /14/ Average Total Losses during Irrigation Season (ac-ft /mile) Summary and Discussion The data presented in this report is preliminary. Additional data collection is in progress and is expected to allow an accurate estimate of water savings by lining canals. 9

11 Preliminary current meter measurement results did confirm the water losses along the Franklin canal. losses ranged form 0.22 to 0.9 cfs per mile or 0.48 to 1.78 per acre-feet per mile per day. There is a great potential for water conservation. The average total water losses for the irrigation season amounts to 269 acre-feet per mile. By lining first 5 miles of the Franklin canal, it is expected to save approximately 1350 acre-feet of water per year, which can supply approximate 400 acre-feet of crop land or over 3000 household for one year water supply. Acknowledgements The author would like to thank following individuals and research programs for their support. Zhuping Sheng, Ph.D., P.E., TAMU, Agricultural Research and Extension Center, Texas Agricultural Experiment Station. Dominic Lannutti, University of Texas at El Paso and El Paso Community College, Bridges Program, K. Reddy, Josh Villalobos, L.S. Aristizabal, TAMU, Agricultural Research and Extension Center, El P aso Texas Agricultural Experiment Station NIH Grant 2R25GM49011 Cooperative State R esearch, Education, and Extension Service, U.S. Department of Agriculture un der Agreem ent No USBR Cooperative Agreement 02-FC= El Paso County Improvement District No. 1. References Blair, A. (2001), Seepage Studies for El Paso Improvement District #1, Technical Memorandum, June Bosman, HH (1993), A method for Discriminating between Evaporation and Seepage Losses from Open Canals. SA WASADV, vol.19, No.2,

12 Sheng, Z. and L. Brown (2002), Franklin Canal Seepage Losses and the Ascarate Lake Diversion, El Paso County Improvement District, U.S Bureau of Reclamation, Texas Resources Institute, Rio Grande Basin Initiative, USDA Sheng, Z. and Y. Wanyan (2003), Seepage Losses for the Rio Grande Project TAMU, Agricultural Research and Extension Center, El Paso Texas Agricultural Experiment Station, El Paso County Improvement District, U.S Bureau of Reclamation, Texas Resources Institute, USDA. Rantz, S.E. and Others, (1982), Measurement and Computation of Stream flow: Measurement of Stage Discharge. Vol. 1, U.S. Geological Survey -Supply Paper 2175: U.S. Government Printing Office, Washington D.C., 1982 Rantz, S.E. and Others, (1982) Measurement and Computation of Stream flow: Computation of Discharge. Vol 2, U.S. Geological Survey -Supply Paper 2175: U.S. Government Printing Office, Washington D.C., 1982 U.S. Bureau of reclamation (USBR) (1997), Measurement Manual. 3 rd. ed.: U.S. Government Printing Office. Denver, Colorado, 1997 Nolan, K. M. and R.R. Shields (2000), Measurement of Stream Discharge by Wading. USGS Resources Investigation Report , Reston, Virginia. 11