Lake Level Discussion

Christopher Dwight's Lake Level Forecast Graph
LCRA Lake Level Forecast Charts
Lake level as of June 24 2009 is 645.28 MSL. The rate of decline has been increasing dramatically in recent weeks. Through the first week of June, the lake had been dropping at 1.8 inches per day, 12 inches per week. Starting on June 08, the rate of decline accelerated to 3.0 inches per day or 21 inches per week. Starting on June 18, the rate of decline accelerated again to 4.1 inches per day or 28 ½ inches per week. At 4.1 inches a day, we can expect to lose 124 inches per month, or 10.3 feet per month. Lake Travis storage is currently 600,428 acre feet (53% full), and Lake Buchanan storage is 512,729 (59% full) for a total storage of 1,113,178 (55% of total capacity).
LCRA water management trigger points - when we reach 900,000 acre feet total capacity, LCRA will request that its municipal customers implement mandatory water restrictions. This may reduce the rate of drop somewhat, though current municipal demands are about 1/3 the amount of water delivered for rice irrigation. There is no restriction on irrigation output for rice farmers until we reach 600,000 acre feet total storage. In terms of lake levels, the rice irrigation curtailment won't kick in until Lake Travis is below 620 MSL. Note that LCRA’s official projection from May 28 forecast approximately 6 feet per month in June, 4 feet per month in July, putting us at 646 at the end of June and 642 at the end of July. LCRA projected approximately 1 foot per month starting in August. This seems optimistic. In August 2006 we lost 5.3 feet, and in August 2008 we lost 3.0 feet. LCRA projected 640 for October 15. I am forecasting 624-625 for October 15. (see below) For past drought years (1984, 2000, 2006, 2008), June is typically our worst month in terms of water quantity lost - averaging 80,161 acre feet for the month. Based on historical averages, we can expect loss rates to decline by 26% in July to 59,086 acre feet, and decline again by 20% in August to 46,985 acre feet. So far in June, we've already lost 111,498 acre feet. By the end of June, I project we'll lose 130,903 acre feet for the month. That's a 63% increase over the average of four drought years. In June 2008 we lost 134,774 acre feet, so it appears our 2009 trends are similar to 2008.

646 MSL currently forecast for for July 02

• Limit of ramp use for many fixed-keel boats (seven feet of water above ramp end)

642 MSL currently forecast for July 25

• Move docks 2 and 3

636 MSL currently forecast for September 07

• Position docks 4, 5, and 6 parallel to shore
• Pavilion moved into North Cove

One key part of the low water plan is to make significant temporary slip reassignments to ensure that boats with recent activity in racing will be able to continue to race during the low water event. The harbor committee is currently working to create the temporary assignment plan.

Another key part of the low water plan is a suspention of Harbor Rule 14 during low water operations (below 646 MSL). Harbor Rule 14 defines the slip usage policy, and possible consequences for inactivity. During this low water event, some members may choose to haul-out their boat rather than risk damage when docks are located offshore. Other members may find their boats in an unusable slip if we reach extreme low water (636 MSL). I have suspended Harbor Rule 14 so that members who choose to haul-out or find their boat in an unusable slip will not be penalized.

Note that several fleets are looking into hiring a crane to allow boats to stay in the water beyond the limit of our ramp use, but still haul-out later during extreme low water. Contact your fleet captain if you are interested in participating.

Lake Forecast

Spotty showers in the hill country have continued to preserve modest inflows into the lakes. Total inflow on Saturday June 06 was 978 cubic feet per second (600 million gallons a day), up from 316 the week prior. Releases from Mansfield Dam have continued to gradually increase...Saturday's release rate was 1,758 cubic feet per second (1.1 billion gallons per day), up from 1,594 the week prior. As of Saturday, June 06, we were losing a net 780 cubic feet per second due to releases, or 504,092,160 gallons per day. This is a substantially lower rate of net loss compared to June 2008 where we averaged 1,463,449,194 daily net gallons lost due to almost zero inflow and even higher release rates.

At current rates, Lake Travis will reach 646 MSL around the end of June. At that level, there is approximately seven feet of water over the end of the North Cove Ramp. For many sailors of fixed-keel boats, the ramp will not be usable much below 646 MSL.

During the low water event of 2006/2007, Lake Travis reached a low point of 643.55 in December 2006. For this year’s low water event, I am forecasting a significantly lower level of approximately 630 MSL by December (barring significant rain).

Note that my forecast lake level is signficantly lower than the LCRA published forecast from June 01. My forecast is based upon 2008 release data, adjusted for current lake levels, with an asumption of continued average inflows

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