The FULL Story about Lake Conroe s Future Water Level of as a Public Water Supply

Transcription

1 The FULL Story about Lake Conroe s Future Water Level of as a Public Water Supply Introduction By Lee G. Cotton, a concerned resident of the Lake Conroe area There has been a great deal of concern among area residents about how planned water withdrawals from Lake Conroe will affect lake levels. The San Jacinto River Authority (SJRA) has addressed these concerns in their publication entitled Solving Montgomery County s Water Shortage (and the Potential Impact on Lake Level) 2, which is available on the SJRA website. This publication presents some of the findings of a detailed study performed in 2010 on how the lake level would be affected by the planned water withdrawals. The SJRA has consistently used these lake level predictions to support their contention that the planned withdrawals will have a minimal impact on lake levels. However, if the full results of the 2010 study were presented, most people would come to a very different conclusion. Executive Summary The SJRA, the government organization in charge of managing Lake Conroe and its development as an area water supply, is implementing its Groundwater Reduction Plan (GRP) for the use of surface water from Lake Conroe to supply Montgomery County s growing needs. The project will be implemented in four phases (first phase will start up in late 2015) that will ultimately withdraw 100,000 acre-feet per year (afpy) from the lake (equivalent to about 4 feet of lake level when the lake is full). The SJRA has published the following predicted effect on lake levels at this ultimate withdrawal rate: The lake level would have been 4 feet or more low for 21% of the time (vs. historically 1% of the time over the period that the lake had existed at the time of the study with only occasional withdrawals), and The lowest lake level would have been 11 feet low during the worst dry period that occurred during (Note: This time period contained dry periods but no severe droughts. The study was performed before the severe drought and has not been updated.) It is not well known nor widely publicized, but the same study that produced the above findings for the period also analyzed how the lake level would have been affected by a severe drought similar to the Drought of Record that occurred in the Lake Conroe region in (and which was somewhat more severe than, but close to, the drought). That study predicted the following lake level behavior: Lake level 4 feet or more low for 30% of the time (over the 56-year study period that included two droughts more severe than any of the dry periods) Lake level 8 feet or more low for 17% of the time Minimum lake level more than 32 feet low during the Drought of Record. 1

2 A 2012 study by Texas A&M researchers to estimate the economic impact on property values, retail sales and sales tax revenue of predicted future lake levels was funded by various stakeholders from the Lake Conroe area. The lake level prediction was used in this study (not the Drought of Record prediction which was available at the time). This study concluded that substantial impacts to residential property values in communities bordering the lake and also to area retail trade based on the projection that the lake would be 4 feet or more low for 21% of the time. How much worse would the economic impact be if the lake is more than 4 feet low for 30% of the time and more than 8 feet low for 17% of the time, as predicted by the Drought of Record study? Recommendations: More public awareness is needed of the severe drop in lake levels that are expected to occur during drought periods as water withdrawals from Lake Conroe ramp up to their planned rates. The economic cost of severe fluctuations of lake level should be re-evaluated in light of the Drought of Record study predictions. Alternative water supplies and methods to stabilize the level of Lake Conroe should be evaluated in light of the high economic cost associated with reduced lake levels. Two such options are to use water from (1) the Trinity River and (2) water wells in the relatively undeveloped Catahoula aquifer. What the SJRA Has Told Us As a part of the front-end planning of SJRA s Groundwater Reduction Plan (GRP), the engineering firm Freese & Nichols, Inc. (F&N) performed a Lake Diversion Study 1 for the SJRA in to evaluate the effect of the planned water withdrawals on lake level. Some of the results of this study have been widely publicized by the SJRA and are summarized in the SJRA publication entitled Solving Montgomery County s Water Shortage (and the Potential Impact on Lake Level) 2. The part of the F&N study that is discussed in the SJRA publication predicts what Lake Conroe s water level would have been over the period 1974 through 2008 (i.e., since the lake was impounded) under four different water withdrawal rates of 25,000, 50,000, 75,000 and 100,000 acre-feet per year (afpy), which correspond to the four development phases of the SJRA s GRP. Figure1 is from the SJRA publication 2 (and from the F&N Lake Diversion Study 1 ). The orange dashed line at an elevation of 201 feet (above sea level) corresponds to the normal lake level (called full pool ). The black dashed line at a lake level elevation of 197 feet corresponds to a 4 foot low lake level, below which lake access and recreational use begin to be impacted. The green line is the historic water level elevation which illustrates the following behavior: The lake level occasionally exceeds the full pool elevation of 201 feet. These events occur after heavy rainfalls and result in water being released from the Lake Conroe dam. The lake level falls below the full pool level during periods of low rainfall, due primarily to evaporation, which occurs constantly and varies with ambient temperature. 2

3 Figure 1 Historical Lake Levels Occasionally, water is released to the City of Houston, which has held rights to 2/3 of the water in Lake Conroe and can use it upon demand to maintain the level of Lake Houston. This occurred once during a dry period in 1988 as shown in Figure 1 and again during the 2011 drought, which is past the time period of the F&N study. Water was released after Hurricane Rita in to maintain a lower lake level to facilitate repairs to the Lake Conroe dam. Fairly small service releases to SJRA customers, such as to maintain level in Entergy s Lewis Creek power plant lake, have had a minor effect on lake level and are not evident in the chart. The lake level was 4 feet or more low for less than 1% of the time during the period that was studied. (Note: The study was completed in 2010 before the drought.) Figure 2, also from the SJRA publication 2 (and the F&N study 1 ), shows the predicted lake level (blue line) if water had been withdrawn at a rate of 100,000 afpy (equivalent to almost 5 feet of lake level when the lake is at full pool), which is the maximum rate planned for the SJRA s GRP and which is expected to occur in 2045 (although it can actually occur much earlier, but more on that later). The following observations can be made from this chart: 3

4 Figure 2 Predicted Lake Level with 100,000 afpy Withdrawal The lake level would have been 4 feet or more low for 21% of the time. The lake would have been 11 feet low (190 foot elevation) during two periods, once during an extended dry period in 2000 and again in 2006 after water was released after Hurricane Rita. Although these predicted water levels would alarm some folks, the SJRA has consistently contended in their various publications and in two one-page advertisements 3,4 published in area magazines that their Groundwater Reduction Plan would have minimal impact on Lake Conroe water levels. This is demonstrated by Figure 3, which is an excerpt from the advertisements 3,4, which are currently available on the SJRA website. Figure 3 Excerpt from SJRA Advertisements What Has the SJRA NOT Told Us? Several dry periods had occurred during the period that is depicted in the above charts, but until the drought, when Lake Conroe s water level fell more than 8 feet low, the lake had not experienced a major drought. Accordingly, the

5 F&N study 1 also included an additional analysis of what the lake level would have been during an earlier period that included the Drought of Record at the various planned withdrawal rates (pages of reference 1, which was obtained directly from the SJRA upon special request; this part of the F&N study has not been widely publicized by the SJRA). Figure 4, which is page 64 of reference 1, shows what the lake level would be predicted to have been if the lake had been in place during the period This time period includes two major droughts prior to 1973, when the lake was impounded. The Drought of Record occurred during the period (see page 46 of reference 1 for more information on the Drought of Record). The green line is what the lake level would have been with no withdrawals. The blue line is the predicted level if with 100,000 afpy withdrawals (every year). Figure 4 Predicted Lake Level with 100,000 afpy Withdrawal Figure 5 is Figure 4 with annotations added to illustrate the following observations: With no withdrawals, the minimum lake level during the Drought of Record would have been 197 feet or 4 feel low. The lake level would drop to more than 32 feet low during a Drought of Record with withdrawals of 100,000 afpy. As shown in Figure 6, which shows the approximate lake boundary when the water level is 32 feet low in red, this would mean a drastic reduction in lake surface area. In fact, all that would remain of the lake north of the FM 1097 bridge would be river bed except for a small area of water less than 5 feet deep. If the rainfall pattern of occurs again, the lake level will be more than 8 feet low for over 9 years total (17% of the study period). 5

6 Figure 5 - Predicted Lake Level with 100,000 afpy Withdrawal Figure 6 Lake Boundary during a Drought of Record (32 feet low) 6

7 Figure 5 also illustrates that no major droughts occurred during the part of the study period, and indeed continuing through 2008, the final year of the part of the F&N study that has been publicized by the SJRA. Another major drought occurred in when the lake level dropped to over 8 feet low for the first time in its history after 48,000 acre-feet of water (equivalent to about 3 feet of lake level when the lake is 8 feet low) was released to the City of Houston in Most folks are familiar with the impacts on recreational use during that period when only three boat ramps on the lake were operational, and businesses around the lake suffered economically. It is not pleasant to think of this occurring for 17% of the time (1 year out of 6). The drought was not quite as bad as the Drought of Record...but it was close. One has to wonder why the SJRA has not extended the F&N analysis to include the drought. It is certainly a question that many concerned citizens have asked. How Has the SJRA Used the Findings of the F&N Study? The results from the portion of the study have been used to support the SJRA s continuing claim that the planned water withdrawal rates will have minimal impact on lake levels, but the SJRA has been very quiet about the findings of the Drought of Record portion of the study. The SJRA has made a wide range of documents that pertain to their Groundwater Reduction Plan available on their website, but Reference 1, which documents the entire F&N study, has not been one of them; it has been available only by special request. How this information would have affected public outcry and overall response to SJRA s GRP when they were selling it during the timeframe can only be conjectured. The portion of the F&N study was used as input to a 2012 study 5 performed by Texas A&M of the potential economic impact of low lake levels caused by the GRP water withdrawals. One task of this study was to validate the findings of the F&N study, but there is no mention of the Drought of Record portion of the F&N study. Following is the Bottom Line Summary from this report: The GRP scenarios are likely to impact lake-levels significantly. Lake-levels are expected to fall more than four feet below full pool 1.6 times more often in phase one than in prior periods, and increase to 8.5 times more often in phase four. Direct economic impacts are most likely to occur geographically near the lake. Residential properties in lakefront communities enjoy a 15% premium, which declines quickly with geographic distance. Residents in lakefront communities expect a 28% decline in residential property values, in which case losses in real estate values would amount to $1.1 billion in the area. For each foot of lake-level decline beyond the first two feet, retail trade revenue in the City of Montgomery decreases about $414,000 per quarter per foot, or about $1.6 million per year per foot. One must wonder if the researchers were given the Drought of Record analysis and what their findings would have been if they had considered lake levels more than 8 feet low for 17% of the time. 7

8 What Is the Future Outlook for Lake Conroe Water Levels? The first phase of the SJRA s GRP for withdrawals for 25,000 afpy has been approved and is being implemented with start-up planned for the second half of Figure 7 (page 58 of reference 1) shows that the 2015 withdrawal rate will have a much less significant impact to lake levels than the full planned development withdrawal rate of 100,000 afpy, even during another severe drought. The minimum water level during the Drought of Record would have been 195 ft. elevation or only 6 feet below normal full pool. It is possible to classify this as good news. Figure 7 - Predicted Lake Level with 25,000 afpy Withdrawal In the bad news category is the fact there has been a long-term trend of increasing regional ambient temperatures and a corresponding trend of more variable, but generally decreasing rainfall. These factors deal a double whammy to lake levels, since increasing temperatures will increase lake evaporation rates at the same time that there is less rainfall to keep the lake full. Heavy rainfall periods, such as experienced in the first six months of 2015, will not necessarily help the situation because, once the lake level reaches 201 feet elevation, all the excess water is spilled downstream. No water gets spilled during a drought when the lake level is below 201 feet. One of the SJRA s frequently used points to illustrate how the GRP will have little impact on the lake is that in an average year, seven feet of EXCESS water spills out of Lake Conroe because the lake is simply full. 2 This fact is irrelevant during a drought and is another indication of how the full story is not being told. 8

9 Also in the bad news category is the fact that population growth in Montgomery County has exceeded predictions when SJRA s GRP was developed and sold, and the 2045 Diversion Rate is likely to occur much sooner than Additionally, it is not widely publicized that the 2045 Diversion Rate of 100,000 afpy could happen much earlier than 2045, if a severe drought occurs. As mentioned earlier, the City of Houston has had rights to 2/3 of the water in Lake Conroe, and they can call on that water to be released from Lake Conroe when it is needed for Houston water supply needs. This has happened twice, during droughts in 1998 and again in According to a 2009 contract between the SJRA and the City of Houston, the SJRA will be able to purchase an annual amount of Lake Conroe water from the City of Houston (based on a nomination made November of the prior year) to supply the planned Montgomery County water supply system. Total withdrawals from Lake Conroe cannot legally exceed 100,000 acre-feet in any calendar year. Since the SJRA holds rights to 1/3 of Lake Conroe or 33,000 afpy, it will not need to purchase any of the City of Houston s water for the first phase of the GRP, which requires 25,000 afpy. Starting with the second phase of the GRP, which requires 50,000 afpy, the SJRA will start nominating and purchasing Lake Conroe water from the City of Houston. Whatever amount of the City of Houston s allotment is NOT nominated by the SJRA is still available for Houston s needs, and would be utilized in a severe drought if needed to maintain Lake Houston s water level. Therefore, during Phase 1 of the GRP ( ), maximum lake withdrawals could be 91,667 afpy (25,000 afpy for the GRP and 66,667 afpy for the CoH). For GRP Phase 2 and onwards (2025+), maximum withdrawals could be 100,000 afpy. Therefore, what the SJRA calls the 2045 Diversion Rate scenario can be expected sooner than 2045 due to population growth, and can happen much sooner if a severe drought occurs. More bad news is the fact that the Volumetric and Sedimentation Survey of Lake Conroe 6, which was performed by the Texas Water Development Board in 2010, found that Lake Conroe had a total reservoir capacity of 411,000 acre-feet, which is 20,000 acre-feet less than the 431,000 acre-feet that was used for the 2010 F&N study. The survey also indicated that approximately 600 acre-feet of lake capacity is lost each year due to sedimentation. The reduced lake capacity will only exacerbate the lower lake levels that will result from the SJRA s GRP withdrawals. What Can Be Done to Save Lake Conroe? The first thing that needs to be done to save Lake Conroe is to get correct information to area stakeholders on what to expect for lake level variations, particularly during drought periods. For 40+ years since Lake Conroe was formed and has had minimal demands on its water withdrawals, the lake has performed like a nearly constant-level lake. Development around the lake, both residential and commercial, has boomed and property values and business plans have been based on that near-constant level performance. The drought introduced us to startling low lake levels when only 48,000 acre-feet of water was released in one year (not 100,000 acre-feet every year). It has generally 9

10 been known that Lake Conroe was developed as a surface water supply reservoir, but the full impact of that use has not been generally understood. Telling the future water level story the way that the SJRA has told it ( minimal impact ) has soothed concerns, but has not helped to identify a situation that needs to be addressed. A major goal of this paper is to inform area stakeholders what to expect for future lake levels, which will be much different that past performance, so that the economic cost of a highly variable lake level can be stewed into the evaluation of options for utilizing Montgomery County water resources. One basic fact involved in lake planning and management is that Lake Conroe has a maximum annual withdrawal limit of 100,000 afpy, and it would take literally an act of congress (the Texas legislature) to lower that value. This value is stated in the Certificate of Adjudication for the lake, with the SJRA holding 33,333 afpy of the annual water rights and the City of Houston holding 66,667 afpy a. The source of the 100,000 afpy limit has not been found by the author of this paper, but is supposedly the volume of water that can be withdrawn from the lake each year such that the full volume of the lake would be utilized during the worst drought that is expected. In other words, 100,000 afpy of water is withdrawn every year, no matter what the lake level is, and the lake would be nearly dry after a severe drought before post-drought rains start to refill it. That performance is similar to what is predicted by the Drought of Record study. Over the years, groundwater from the Gulf Coast Aquifers has been the primary source of public water in Montgomery County. The Lone Star Groundwater Conservation District (LSGCD) has been established for the purpose of conserving and protecting groundwater resources in the county. Based on extensive computer modeling of the Gulf Coast Aquifers, the LSGCD has set a limit of 64,000 afpy limit on groundwater produced from these aquifers within the county. Full implementation of the LSGCD s requirements is required by January 2016, by which time the first phase of the SJRA s GRP will be fully operational. The LSGCD plans a monitoring program to assess the effect of the reduced withdrawals on the aquifers with a first assessment to be completed by the end of Whether this will result in any change in the 64,000 afpy aquifer limit (up or down?) is anybody s guess. A higher limit would be nice since it would tend to reduce withdrawals from Lake Conroe, but, at best, this would only defer the ever-increasing withdrawal requirements from the lake. (Note: The 64,000 afpy limit is being contested by various groups, including the Lake Conroe Communities Network, a non-profit organization of area residents, homeowners associations and municipal districts. See their website for more information.) One potential remedy to save the lake that is frequently mentioned is to cancel the future planned phases of the SJRA s GRP facilities. However, even if the ultimate capacity of the GRP facilities was restricted to the first or even the second phase (25,000 or 50,000 afpy), the lake would still be subject to a total withdrawal rate of 100,000 afpy that could be utilized in drought periods. The CoH still holds 66,667 afpy water rights that are available to them if the SJRA does not purchase them, and the portion of the CoH water a As explained earlier, the SJRA has contracted with the CoH to purchase an annually nominated portion of the CoH s water rights as needed to feed the GRP facilities. 10

11 that the SJRA does not purchase can be used by the CoH to feed Lake Houston, particularly during critical drought periods. Therefore, the author believes that the future phases need to proceed, albeit with the caveat that the approval for future phases needs to be contingent upon the evaluation of alternative sources of water to be used during drought periods to preserve lake level. What alternative sources of water are available to Montgomery County, other than groundwater from the Gulf Coast Aquifers and Lake Conroe? After the LSGCD established its 64,000 afpy groundwater limit, the SJRA undertook a Water Supply Potential Source Study 7 to identify alternative water supply sources for Montgomery County. Nine alternatives were screened which included such things as trading or purchasing various water rights with the City of Houston and the Trinity River Authority, purchasing treated water from Harris County and various methods to get that water into Montgomery County. Five of the nine options dropped out based on a screening evaluation, and the following four options were evaluated in more detail: 1. Install water treating facilities that are supplied by water from Lake Conroe in Use SJRA Lake Conroe water rights for the initial phase and contract for City of Houston water rights for the 2025, 2035 and 2045 expansions. (Note: This option was adopted by the SJRA for the GRP and is in the final stages of being implemented.) 2. Install water treating facilities that are supplied by water from Lake Conroe in Use SJRA Lake Conroe water rights for the initial phase and contract for water from the Trinity River Authority (TRA) for the 2025, 2035 and 2045 expansions. The TRA water would be sourced north of Lake Livingston and be pumped and piped into a canal that would gravity flow into the north end of Lake Conroe. The CoH would presumably retain and possibly use their water rights for 66,667 afpy from Lake Conroe. 3. Install water treating facilities that are supplied by water from Lake Conroe in Use SJRA Lake Conroe water rights for the initial phase and contract for water from BOTH the Trinity River Authority and the CoH for the 2025, 2035 and 2045 expansions. The TRA water would be sourced north of Lake Livingston and be pumped and piped into a canal that would gravity flow into the north end of Lake Conroe and would be used to replace water taken withdrawn from Lake Conroe and thereby stabilize its level. 4. Contract for imported water from north Harris County for surface water requirements through Install storage and distribution facilities to deliver water to the Woodlands and Conroe. Lake Conroe is not used as a surface water supply. Option 1, the option that became SJRA s GRP, was selected due to lowest cost, even though it would have the highest impact on Lake Conroe water levels. There was no economic value placed upon stabilizing Lake Conroe water levels, as options 3 and 4 would do. However, Option 3, diversion of water from the Trinity River, is still available if public outcry forces the SJRA to consider the economic cost associated with low lake levels during drought periods. The Catahoula aquifer, which is not regulated by the LSGCD, was not considered as a potential source by the SJRA in 2009, when the above Water Supply Potential Source 11

12 Study 7 was performed. It is not even mentioned in the report. The primary reason for this is that at that time there were very few Catahoula aquifer water wells in the Montgomery County area and not much information was available to confirm that it was a reliable, long-term water supply source at rates that the county would need in the future. Since 2009, a number of municipalities and utility districts have drilled high capacity water wells to the Catahoula aquifer in order to avoid high pumpage fees that are charged for water produced from the traditional Gulf Coast Aquifers (and which provide partial funding for the GRP facilities required to utilize Lake Conroe surface water). The Catahoula aquifer is deeper than the Gulf Coast Aquifers and its water is brackish and requires cooling in the southern part of the county. However, the Catahoula aquifer is shallower in the northern part of the county where it is cooler and sufficiently fresh such that it is successfully being used without special treating or cooling. Utilization of groundwater from the Catahoula aquifer offers a potentially low cost option as a future water supply source for Montgomery County or for simply stabilizing the level of Lake Conroe during droughts. Recommendations Public and business awareness of the true probable impact on Lake Conroe of the full development of SJRA s Groundwater Reduction Plan needs to be increased. The F&N study should be extended to evaluate what water levels would be predicted during the drought at the planned GRP withdrawal rates. The Texas A&M economic impact study should be re-visited using lake level predictions from the Drought of Record study and from extending the F&N study through the drought of Alternatives to stabilize and maintain future Lake Conroe water levels need to be evaluated in light of the re-evaluated economic impacts (e.g., accelerated Catahoula aquifer development, Trinity River diversion). 12

13 References Note: These documents are all available on the website SaveLakeConroe.com. 1 Lake Level Presentation_Public Handout_FINAL.pdf from the Lake Diversion Study performed by Freese & Nichols, Inc. in (obtained from the SJRA by special request) 2 Solving Montgomery County s Water Shortage (and the Potential Impact on Lake Level by Jace A. Houston (.pdf version available on SJRA website) 3 SJRA FullPage Quench AD (.pdf version available on SJRA website) 4 SJRA FullPage Level AD (.pdf version available on SJRA website) 5 Impact of Lake-Level Reductions on Lake Conroe Area: Lake Area Property Values, Property Tax Revenues and Sales Tax Revenues, G. O. Rogers, et. al., July 2012 (formerly, but no longer available on SJRA website) 6 Volumetric and Sedimentation Survey of Lake Conroe, Texas Water Development Board, July Water Resource Potential Source Study, Montgomery County Alternative Water Supply Program, SJRA, January 2009 (.pdf version available on SJRA website) 13