Drought Level II Precursor to Accelerated Pumping

Item #16 on the agenda for Tuesday's City Council Meeting is:

Consideration of adopting a Resolution implementing Drought Level II of the City’s Water Conservation and Drought Contingency Plan
(Presentation by Director of Water Utilities Will Wilde)

Water Chief Will Wilde's memo to council states:

Based on the water supply currently available to the City, the criteria for entering Drought Stage, Level II, are met.

The South Pool at Twin Buttes is up three to four feet from October 2011.  The North Pool  is down more than that, despite water flowing through the Equalization Channel.

What changed that the City suddenly qualified for Drought Level II, now vs. last November?  San Angelo's Ivie allocation was cut in half.  Enjoy the South Pool now.  The City plans to pump it away.  It's clear from the March 20 minutes.

SELECTION OF GAJESKE, INC. FOR RFP WU-02-12 LAKE PUMPING SYSTEM TO TRANSFER WATER FROM THE SOUTH POOL OF TWIN BUTTES RESERVOIR TO THE NORTH POOL AND AUTHORIZATION FOR THE INTERIM CITY MANAGER OR DESIGNEE TO EXECUTE ANY NECESSARY RELATED DOCUMENTS

Water Utilities Director Will Wilde presented background information. General discussion was held on the project timeline, aquatic life within the pools, existing pump and natural movement of the water, water storage capacity, project not approved during the budget process; providing vendors experience, including other projects completed; designating the water fund as the funding source, and
evaporation of the water.

Mr. Wilde informed staff is preparing to begin the project in June depending on the amount of rain received between now and then and in the event of the Stage II Drought Conservation Plan. He noted the vendor is aware the project may or may not occur.

Council directed staff to present an accelerated schedule should Council want to proceed sooner.

Motion, to approve, as presented, was made by Councilmember Hirschfeld and seconded by Councilmember Alexander. Motion carried unanimously.

Mr. Wilde informed staff will present a future budget amendment, and then further action will by City Council to begin the project.

A vote was taken on the motion on the floor. AYE: New, Alexander, Silvas, Adams, and Hirschfeld. NAY: Morrison and Farmer. Motion carried 5-2.

I only read one motion, yet there were two votes.  That's about as clear as Twin Buttes water.  Without Ivie to shoulder the load, Twin Buttes is it.  Pray for rain.

Formula One Windsurfer Sails South Pool

I had a treat today while windsurfing the South Pool.  Kirk, a Formula One windsurfer from East Texas, tested our West Texas winds.  Formula One is a racing class of sailboards.  Boards are wider and fins longer than One Design racing gear (the era of my sailboard racing).

Kirk kicked off his racing duds for an afternoon of play.  Kirk sailed a 6.2 square meter North Sail, while I had a 5.5 Neil Pryde.  As West Texas winds go, we had the right sail size, at least part of the time.

We both had roughly 100 liter boards but mine looked like an antique .  Kirk's fin was double mine.  A few gusts rattled just about everything on my rig.  Several lulls tested my board balance, shoulder strength and grip endurance.  It's actually harder to sail underpowered on high wind gear.

While the day started rough with a harness line snapping, it finished in fine form. Near the end of the day, Kirk blew by me.  He had a hold of a cantankerous West Texas wind gust.  I recognized it, having ridden a few myself.  I had a blast on the water.  Sleep, it'll come easy tonight. 

P.S.  My apologies, I didn't think about taking any pictures today.  The image above is from October 2011.  The South Pool is probably 3-4 feet higher today.

Lack of Runoff for Twin Buttes

I walked the banks of the Middle Concho yesterday, hoping to hear the river roar. Over the weekend heavy rains near Barnhart washed away a pickup truck. Fortunately, the driver escaped safely from the raging river, suddenly a 150 to 200 feet wide torrent. 

From the data above, none of that runoff made the North Pool at Twin Buttes, which is fed by the Middle Concho.  Or, if it did, the City has been letting it (and more) flow through the gate at Twin Buttes.

Pressure Grows on Twin Buttes

The Standard Times reported:

The drinking water allowance allocated to the city of San Angelo from the O.H. Ivie Reservoir was cut by 30 percent this month.

San Angelo will need to make up the difference by drawing more from local reservoirs.

That means Twin Buttes.

The San Angelo City Council voted this week to take steps toward pumping water out of the South Pool of the Twin Buttes reservoir and putting it into use since water becomes trapped in the South Pool after it is drawn down past a certain elevation, thereby leaving about a month's worth of water out of reach.

The City plans to pump South Pool water in June, a time of high heat and evaporation.

"Since we'll be relying more on our local sources, to gravity feed down to the water plant, we'll have to start utilizing everything we can from Twin Buttes," said Will Wilde, the city's director of water utilities.

It will gravity feed the water, meaning dry soil and water wicking plants will have their chance to violate the city's assumption:

No water will be lost in the transfer process from the south to north pool..

The City can build a pipeline to Hickory, but can't get South Pool water to the treatment plant without loss?  Something strange is going on.

Councilman Paul Alexander says not to worry about the South Pool:

One medium rain, and that lake (South Pool) will fill up overnight. It takes about 90 days to drain that pool, so we are way behind in schedule. We should be pumping starting April 1st at the latest.

How did last night's rain impact Twin Buttes?  It looked like a medium rain across the Twin Buttes watershed on radar.  This morning's flow looked like:

As for the city's projections on less evaporation, they assume water can be shifted from one pool to the other instantaneously.  They show the South Pool's 520 surface area acres added to the North Pool's 882, bringing the North Pool's surface area to 1093 acres, then show a year's worth of savings.

In reality, that process takes "about 90 days" and will occur during our high evaporation months.  As a result, evaporation savings will be much less than the projected 1622 acre feet.

With our Ivie drinking water down and O.C. Fisher barren, Twin Buttes is it.  .

Update 4-9-12:  Twin Buttes elevation is reported unchanged by the Bureau of Reclamation.  Hopefully, the runoff is upstream, working its way down.

Raise North Pool Five Feet: Less Than Amount Lost to Annual Evaporation

Councilman Paul Alexander shared the city's study on pumping the total volume of the South Pool into the North Pool at Twin Buttes.  It turns out the North Pool will rise by 5.15 feet, while annual evaporation is 5.25 feet, the vast majority of which occurs during the summer. If the whole amount of the transfer stands to be evaporated over a year's time, what are the savings? 

April 2, 2012 Evaporation savings by moving water from South Pool to North Pool at Twin Buttes

Assumptions:

1) current levels of both pools as of 4/2/2012,

2) no loss of water in the transfer from the south to north pools.

Twin Buttes Reservoir

ELEVATION(FT) AREA(ACRES) VOLUME(ACRE-FT)

North Pool 1890.65’ 882 8,170

South Pool 1925.78’ 520 5,028

Total 1,402 13,198

Projected with observed south pool transferred to north pool

North Pool 1895.8’ 1,093 13,198

Projected change in water surface area (1402-1093) = 309 acres

Approximate annual average evaporation is 63 inches/year=5.25 feet

Change in water evaporated: 309 Acre Feet * 5,25 feet = 1622 acre feet per year.

These numbers are approximate and apply with the assumptions made.

The reality is the dry 211 acres in the North Pool will absorb some amount of South Pool water.  How much thirsty vegetation grew on those 211 acres?  This came from a Twin Buttes Brush Control Study from April 2010:

One acre of saltcedar on the Pecos River of Texas was estimated to use 5-7 acre-ft. of water every year (Hart 2003). The longer saltcedar occupies an area, the drier the area becomes. Saltcedar currently dominates 1,092 acres in the project area (Twin Buttes).

Councilman Alexander believes a few modest rains will rapidly refill the South Pool.  We've had modest rains since October and the South Pool is up about two feet.  What happens when the South Pool is completely drained, as in the city's assumption?  Will the spring fed South Concho keep its flow?  How much thirsty vegetation will grow on the South Pool lake bed?  How will that impact a "modest rain's" ability to refill the South Pool.

The City frequently offers crude analysis to push their desired strategies.  This got play in August last year, then became embedded in a consent agenda.  The public, especially users of the South Pool, deserve better.

I understand the city needs water.  It should pump what it needs to in the most efficient and effective way possible.  If it can build a pipeline to pump Hickory water, it should be able to do the same from the South Pool.  Rather than assume no loss, it should guarantee such.

This issue arose in 2004.   Why didn't San Angelo's Water Czar make recommendations to utilize South Concho River water effectively in a time of drought?  What impact did agricultural commitments have on such plans?

Much of the stored water is used to irrigate 10,000 acres of crop and rangeland (Reclamation 1994).

How did the Water Czar's "hobby farm," which draws water for irrigation from the South Pool, enter into consideration?  The public won't know.  That topic is off limits.

Update 4-7-12:  Councilman Alexander's medium rain may be in the offing.