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Canyon Lake
Daily Flow Rates Water Resource

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Canyon Lake Statistics (return)

Earth Dam
 Completed in 1964
Surface area = 8240 acres
 Normal Storage = 386,200 acre feet
 Maximum Storage = 1,129,300 acre feet
 Maximum Discharge = 502,800 cfs
 Drainage area = 1425 square miles
 Dam Length = 4410 ft
 Dam Height = 224 ft

What Do the Flow Numbers Mean

Click Here for Canyon Lake Elevation Webpage  

At the Army Corps of Engineers Ft Worth District webpage click on Hydrologic Data.  Then select Canyon Lake and click Get Data button

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Maximum Discharge
Number of cubic feet per second (cu ft/sec) which the spillway is capable of discharging when the reservoir is at its maximum designed water surface elevation.  (Maximum Flood of Record is less than 100,000 cfs). 

Maximum Storage
Maximum storage, in acre-feet, which is defined as the total storage space in a reservoir below the maximum attainable water surface elevation, including any surcharge storage.

Normal Storage
Normal storage, in acre-feet, which is defined as the total storage space in a reservoir below the normal retention level, including dead and inactive storage and excluding any flood control or surcharge storage.

Source - Army Corps of Engineers Website

 

What do the numbers mean? 

River flow is given in cfs (cubic feet per second),
Pumping rates in gpm (gallons per minute)
Water allotments to water companies in acre feet per year. 

News paper articles usually note that one acre foot is equal to 325,851 gallons or the normal amount of water used by two families of 4 in a year.   That is a little less than 450 gallons a day or 13,500 gallons a month per family.

But what does it mean when Canyon Lake water supply is allotted 4000 acre feet per year of water from Canyon Lake or GBRA is granted another 40,000 acre feet per year of Canyon Lake water?  What flow rate is needed from the Guadalupe River to replace that water?

What does it mean when Southeast Trinity Underground Water District is given permitting authority on wells that pump over 17 gpm?

These tables will help answer these questions for you. 

Equivalents

   Equivalents
Cubic foot Gallons Acre foot Cubic Feet Gallons
1 7.48 1 43,560 325,851
Equivalent Flow Rates
cfs gpm Acre ft/day Acre ft/yr Billions of Gallons/yr
1 449 1.98 724 0.24
10 4,488 19.8 7,240 2.36
100 44,883 198 72,397 23.59
1000 448,831 1983 723,967 235.91
0.038 17 0.08 27 0.01
0.223 100 0.44 161 0.05
0.446 200 0.88 323 0.11
2.228 1,000 4.42 1,613 0.53
0.0014 0.62 0.003 1 0.0003
0.138 62 0.274 100 0.03
13.8 6,200 27 10,000 3.26
69 30,998 137 50,000 16.29
124 55,796 247 90,000 29.33

 

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