Hydrology Study 2013-2014 Medina Lake, Texas Prepared by Mike Crandall 2014

Location- From Medina Lake Spillway to Diversion Dam Medina County, Texas

Date of Study- January 2010 through January 2014

Table of Contents *Introduction *Hydrology at the Medina Dam *Medina Dam Gate Valves *Hydrology of the Medina Lake Spillway/Mexican Draw *Skull Springs Pool *Skull Springs Weir Pool *Hydrology of Skull Springs Weir *Hydrology of Diversion Lake *The Diversion Lake Fault *Hydrology of the Diversion Dam *The Canal Gates *Metering Devices in the System *Conclusion *Appendix

*Figure index 26-Figure 1- Elevations drawing of system 27-Figure 2- Elevations drawing of system 28-Figure 3- Elevations graphic of system 29-Figure 4- Balcones and Diversion Lake Fault

*Photo index 30-Photo 1- Google aerial of north section of system 31-Photo 2- Aerial of north section of system 32-Photo 3- Aerial of south section of system 33-Photo 4- Aerial of Diversion Dam overtopped 34&35-Photo 5&6 - Canal gates at Diversion Dam 36-Photo 7-Canal gates up close 37-Photo 8- Skull Springs Weir *38thru44 More Information on Medina Lake *46thru48 Medina Lake DVD's Introduction Hydrographic Survey Report Mike Crandall conducted an independent report on the water hydrology/conveyance system, at a location between the Medina Dam and its Spillway and the Diversion Dam. This system was engineered and designed by Dr. Fred Stark Pearson. This is approximately a 4 mile section of the Medina Lake conveyance system. Starting at the Medina Dam and Spillway, then following the Medina River downstream to Skull Springs Pool, Skull Springs Weir Pool, Skull Springs Weir, Diversion Lake, Diversion Lake Fault, Diversion Dam, and the canals, in that order.

Hydrology at the Medina Dam The Medina Dam is 1580 feet in length at the top, 164 feet tall, and 23 feet wide at the top with its top elevation at 1076 feet above sea level (ASL). The Dam is located in Mico, Texas in Medina County. Below the Medina Dam there are 122 relief wells to relieve upward pressure on the dam. These relief wells exit water downstream of the Medina Lake Dam, and there are many springs which naturally feed the river downstream. The Medina Dam has 2 gate valves to control water flow to the conveyance system. During high Medina Lake levels, natural springs flow under and around the Medina Dam and feed the river downstream with great amounts of water. During low Medina Lake levels these natural springs decrease their volume of water going around, under, and downstream of the Medina Dam.

Medina Dam Gate Valves At the Medina Lake Dam gate valves there are no meters for monitoring the amount of water coming out of the gate valves and leaving Medina Lake. The Bexar Medina Atascosa Water Improvement District #1 (BMA) is in control of the gate valves at Medina Dam. These gate valves were recently replaced in 2004 by ASI Dam and Water Resource Constructors with 36" and 48" throttling knife gate valves. The original gate valves were in working order when the Dam was built, but through the years they eventually became inoperable. Before the replacement of these gate valves they could not be shut, resulting in great water loss from Medina Lake for many years. Dr. Fred Stark Pearson installed the gate valves at the Medina Dam for water control adjustments. The purpose of these gate valves are to be a water measuring device, to conserve water and control the water flow to Skull Springs Weir, and into the canal gates. The valves should be monitored and adjusted to keep the water from overtopping the Diversion Dam, and to ensure proper water level at the canal gates at Diversion Dam.

Hydrology of the Medina Lake Spillway/Mexican Draw The Medina Lake Spillway Crest is 1064 feet ASL, according to the National Archives and Records Administration (NARA), which is 12' below the crest of Medina Lake Dam. The spillway length is 880 feet next to the Medina Dam on its northwest side. The spillway is designed to keep the Medina Lake Dam from being overtopped with flood water. During floods it releases water into the Mexican Draw that feeds back into the Medina River downstream at Skull Springs Pool. Even when the spillway is not flowing over its crest, the Mexican Draw still provides great amounts of water in the form of natural springs to Skull Springs Pool, and the downstream flow.

Skull Springs Pool Skull Springs Pool is directly behind the Medina Dam and is fed by 1) natural springs, 2) 122 relief wells under Medina Dam, 3) Mexican Draw/spillway, and 4) the Medina Dam gate valves. From Skull Springs Pool water flows downriver under the CR 271 bridge to Skull Springs Weir Pool. Skull Springs Weir Pool Skull Springs Weir Pool is upstream of Skull Springs Weir. This pool is only seen as a pool when water is not overtopping Skull Springs Weir. When water overtops the weir Skull Springs Weir Pool becomes part of Diversion Lake.

Hydrology of Skull Springs Weir Skull Springs Weir, designed by Dr. Fred Pearson, is defined as a rectangular broad crested weir with a 23 inch shoulder and 1 submerged gate. This weir functions as a water measuring device for water flow. This weir is located approximately 1.4 miles downstream of Medina Dam. The Medina Lake gate valve adjustments have a tremendous impact on the water flow over this weir. Water flow over this weir corresponds with flow into the canal gates at the Diversion Dam. When the water is flowing 1/8 inch over the crest of this weir it sends water into the canal at a level of approximately 8 inches. When the water is at the top of the shoulder (23 inches above crest) it sends water into the canal at a level of 2 feet 7 inches.

Hydrology of Diversion Lake Diversion Lake is the final stage of the conveyance system that takes water to the canals at Diversion Dam. The Diversion Lake is a reservoir on the Medina River; it is approximately 1.4 miles downstream of the Medina Lake Dam and eleven miles north of Castroville in northeastern Medina County (at 29°31' N, 98°54' W). This lake is approximately 3 miles in length and 400 acres in size and has a normal capacity of 4,500 acre-feet and a maximum capacity of 16,199 acre-feet. The water level on Diversion Lake can be adjusted by the Medina Lake Gate Valves. In the Diversion Lake area there is a fault known as the Diversion Lake Fault. This fault, and porous limestone, does directly affect the Edwards Aquifer by supplying additional water. The Diversion Lake Fault This fault is a primary fault and part of the Balcones Fault Zone. The Diversion Lake Fault runs through a section of the Medina River in the Diversion Lake area approximately 2 miles upstream of the Diversion Dam (Photo 3). Reported from the USGS investigations report 00-4148, the Diversion Lake area and the Diversion Lake fault have a consistent seepage of 1500 acre feet per month into the Edwards Aquifer. Hydrology of the Diversion Dam The dam was completed in 1913 at a cost of $288,000. The Dam is used mainly to divert water for irrigation. It is located approximately 4 miles south of Medina Dam. The reservoir (Diversion Lake) was constructed to avoid the expensive and difficult engineering required to build an irrigation-canal system in 1912 through the rugged canyons of the Medina River immediately south of Medina Lake Dam. The Diversion Lake water level in turn controls the flow and amount of water released into an extensive irrigation system (canal system). The solid concrete dam, fifty feet high and forty-four feet wide at the base, is 440 feet long. The top elevation of its crest is 926 feet ASL according to NARA. The Diversion Dam is also the spillway for Diversion Lake and has two gate valves at its base. There are many natural springs that flow around and under the Diversion Dam that supply water to the Medina River downstream of the dam. The Diversion Dam is not meant to have water overtopping its crest except during floods.

The Canal Gates The canal gates are located at the Diversion Dam at its northwest side and have a height of 11 feet at the inlet. After going through the inlet gates the water hits 5 individual gates that are designed to open or close individually and send water into the canal itself.

Metering Device In The System In 1912 Dr. Fred Stark Pearson had only 1 way to measure water flow in his system. This was by use of weirs. Pearson placed Skull Springs Weir strategically where it is located to measure and control water in his system. Skull Springs Weir is still, as of today, the only instrument currently in place to measure actual water flow in the system described above.

Conclusion The system is not being used as designed and consequently is wasting water. Medina Dam Gate Valves are not being properly monitored and adjusted to prevent water being wasted by freely flowing over Diversion Dam. Proposed Solution: The controlling entity has a responsibility to conserve water as a vital natural resource and properly maintain the Medina Lake and downstream system supplying the canals in a proper manner. This would require constant monitoring and adjusting of the system.

Appendix - 1 acre foot of water equals 1 acre of land covered with water to a depth of 1 foot.

- 1 acre foot of water equals 325,851 gallons

- ASL – above sea level

- Weir – a low dam built across a river to raise the water level, divert the water, control its flow or as a water flow measuring device.

-Hydrology – the branch of science concerned with the properties of the earth’s water, especially its movement in relation to land.

-Dr Fred Stark Pearson- (1861– 1915)

Frederick Stark Pearson, civil engineer, son of Ambrose and Hannah (Edgerly) Pearson, was born in Lowell, Massachusetts, on July 3, 1861. He graduated from Tufts College in 1883 and received a Master's degree in 1884. Later he was awarded honorary Doctor of Science and Doctor of Laws degrees (in 1900 and 1905). He was a professor of mathematics and applied mechanics at Tufts from 1883 to 1886. Pearson developed the Electric Transportation System in Boston and in 1894 became Chief Engineer of Metropolitan Street Railways in New York City; he served as consulting engineer for other street railway systems in Canada, the United States, Cuba, and England. He developed electric power systems for São Paulo and Rio de Janeiro, Brazil, Mexico City, and Winnipeg, Manitoba. In 1911 he was Chief Engineer of the building of the Medina Dam on the Medina River in Texas and established an irrigation district of more than 35,000 acres in Bexar, Medina, and Atascosa counties.

Prepared by Mike Crandall 2014 Assumptions in the above study are based upon available research and observations over a 22 year period. 210-859-5246

MEDINA LAKE MAIN DAM OUTLET GATE REPLACEMENT Mico, Texas USA

Fast Facts NOTABLE ASI Role: FEATURES General Contractor Type of Dam: Mass Concrete, Gravity Dam ? Hydro-demolition of outlet structure Dam Height: concrete. 164 feet ? Slip-lining of 66 inch Crest Length: steel outlet pipes with 1,580 feet 54 inch steel liner. Conventional Concrete: ? 3-stage annular grouting. 200 cy Contract Value: ? 48 inch and 36 inch throttling knife gate $1,230,000 valves.

PROJECT HIGHLIGHTS This project involved modifications to the regulating outlet works of an existing dam constructed in 1912.

The project work included underwater and marine work to repair the existing 7 ft x 7 ft sluice gates, and replacement of stems and guides. It also included gate operator replacement; 100 cy concrete hydro demolition; 165 cy structural concrete demolition; placement of 200 cy structural concrete; 158 ft slip-lining of existing 66 inch steel pipe with 54 inch steel liner pipe; annular grouting; installation of new knife gate valves; repairs of outlet transitions; electrical work; Reference / and access road improvements. Owner: Bexar Metropolitan Water District P.O. Box 245994 San Antonio, TX 78224 Larry Bittle (210) 354-6500

ASI Completion Date: April 2004

ASI Job Number: Job # 11-0304

Built to Last.

ASI Constructors, Inc. 1850 E. Platteville Blvd.; Pueblo West, CO 81007 T. (719) 647-2821 F. (719) 647-2890 www.asiconstructors.com

300,000 \ 700 \ 270.000 1,400

240,000

2,100 \ 210,000 \ ^ 2.800 a x 180,000H g UJ g. 13,500 (.)

JI 150,000E \ (.) * 4,200 $ l o 120,000 \ 4,900 I 90,000

5,600 \ 60,000

6,300 K \ 30,000

7,000 I 0 't,050 975 990 1,005 1,020 1,035 1,065 1,080 1,095 ELEVATION(FEET)

SURFACEAREACAPACIry ---x--- MEDINALAKE July1995 SURVEY PEpacd by: TWOB Apni 1996

© Mike Crandall 2014 7162 CR 271 Mico, Texas Phone- 210-859-5246 email- [email protected]