Questions Based on Presentation Handout: You make the statement that the Upper Glen Rose "confines" the aquifers below the Upper Glen Rose and that almost all recharge to these aquifers comes from Gillespie and Kimble Counties. What proof to you have of this ? How do you know rechazge does not go through the Upper Glen Rose through fractures or other means ? What recharge percentage have you incorporated in your model What population projection figures does HGCD use ? The state estimate or some other estimate. What aquifers are included in the HGCD GAM you are building ?Does this include all aquifers that produce potable water in Kerr County ? Exactly where are the 22 monitor wells and what aquifers do they monitor and do they all monitor all aquifers ? Do you have a chart that shows the exact location of each monitor well that also shows the aquifer that each well monitors ? There are numerous shallow wells through out the county especially along the rivers and streams. What aquifers aze these wells producing from ?Are they incorporated in your model ? How many of the existing wells in Kerr County are in the well database ? How many wells have been drilled in the past ten years ?How many of these wells aze in the Middle Trinity ?Lower Trinity ?Are all wells drilled in the past 10 years in the GAM ? How many deep wells has HGCD logged to date ?How many wells does HGCD have logs on ? Why does your GAM have "1 O layers" What is included in a layer ?How do you decide what data goes in a cell if there are no wells in the cell ? Do all cells get the same data. How did you decide what data goes into a cell ? How does the GAM model reconcile the differences in cell data when you aze working with multiple aquifers with different chazacteristics ? How many assumptions do you make when filling a cell ?How do you keep track of cells with estimated data versus actual data from a actual well ? What does it mean that you have finished "subsurface geometry and flow dynamics" ?How many wells were used to create this information and where are these wells ? You state several times that the subsurface geology in Kerr County is very complex and changes from point to point very rapidly. How do you incorporate this into your model ? The previous GAM's done by the TWDB seemed to take a great deal of time to complete with large staffs working on the models. How can you do this GAM with so much more detail with little staff ? By your graphs and charts it appears much of the data you are using is just taking current data from other entities and then putting your name on the data. How much of the new GAM is actually new data ? When will the model be complete ?Upon completion how many cells will actually reflect data from actual wells ? General Questions: How many cross sections have you developed and where are they ?How many of the aquifers are included in your cross sections ? How can you make one model for Kerr County when the aquifers in the western part of the county and the eastern part of the county are so different and from completely different aquifers ? At this time how accurately can you predict water availability by aquifer for a new proposed well ? Is the accuracy the same throughout the county ? Headwaters was created through the legislative process in 1991 It is one of 89 groundwater districts that fill all but about 90 out of the 254 counties of the state Headwaters primary goal is groundwater conservation Five elected board members, four employees and one geologic consultant form the staff of Headwaters Priorities of Headwaters include: 2 Before we move into the implementation of the objectives, a little bit of back ground information may help us understand how groundwater moves and is recharged The Water Cycle moves water vapor from the Gulf of Mexico and the Pacific into the atmosphere. It remains in the atmosphere for about two weeks and then falls back to the Earth as rain, fog or dew. 2/3 rds of Kerr County is covered by the cavernous Edwards limestone and a fair amount of rainfall falls into the fractures and holes on the western side of the county and drains out as pristine spring flow. Some of the spring flow originates beyond the county boundaries The age of the water in the subsurface for all of the aquifers ranges from less than 100 years to several thousand years. 3 ~ , /( ~~ 1 / ~ O~ .y ~ 1 1 1 . /_._..__.. .. i .. _,,.,_ _ I d '" 1 1 ~y ~ a w ~ 1 1 1 1 I ~ 1 ....._..., _ 1 1 . ~ 1... _.... - f _ $~ / ~ Q ~. 9e to - w ~ l "~'T \ `~ L~~ a~Cl ~~ ~ ~~ ~~ -water IIOVr o rlfSCharlJe f0 ~~ ~~a _ 1 -T ~ r 0 ~ ~' '-" o A alluvium ~~ II ~_sawrat- jzonre T ~ ° ~ T - _-~_ T T• Another water cycle view of the interaction with groundwater 4 -~ Dry ~ow.pm~i a.ep Sat'ted me am«oo.ptl w ~.. i....~ r.u Hensel ]O miba 833 We9M mow 5280'? ~_c~ ~ 100 BP ~~ \VI ""~ 25,000 BP a .y ..mr.n.i m. Saturated ew.«w.. w,,,,,,, Hensel aaw,. e..m.m.ntl imp mp wen. mew, em m. wab. maleaMa move very elavily tlawn gnGMm Rainfall recharges the outcrop and then slowly moves molecule-by- molecule into the subsurface over hundreds and even thousands of years Before Present (BP) The water level in your well moves up or down by the pressure of the ;~ water at the outcrop in the confined portions of the various aquifers and not from the rain that falls on the surface today The entire county is covered by a confining blanket of clay and marl known as the Upper Glen Rose, which lies below the Edwards The Edwards lies at the higher elevations and the Upper Glen Rose lies below the Edwards and confines all of the other aquifers below. Almost all of the recharge to the underlying confined units is derived from Gillespie and Kimble Counties 5 A confined aquifer depicting pressure induced water levels 6 What are we specifically trying to achieve? These are some of the questions that we have attempted to answer and it is an on-going process. How can we approach and unravel the subsurface geology and explain how the water moves through the subsurface? a Sustainability implies that recharge will occur within the lifetime of mankind The yield spectrum as depicted on this slide displays a full slate of possible production objectives ranging from complete mining to no pumping at all Note the definition of "safe yield" is a point on the spectrum where recharge equals discharge Sustainable yield might fall between safe yield and no pumping at all It is up to policy makers to decide where they wish to end up on the spectrum on an aquifer-by-aquifer basis s How will the population growth of Texas impact Kerr County 50-years from now? Thus far, the population of Kerr County has tracked the growth of the state's population growth 10 The Texas Water Development Board predicted that the population of Kerr County will level off or even decline after 2030 Kerr County has no history of leveling off. 11 The concept of groundwater moving through the subsurface falls into the realm of the occult for many people Indeed, the movement of groundwater is very complex as it seeps through the subsurface through a series of tiny connected holes referred to as porosity, hydraulic a conductivity and something else called transmissivity A groundwater model is only as good as the quality and quantity of data that is put into the model Two years ago Headwaters launched a program to build a county wide groundwater model. Much of the model is based upon pre-existing data with new interpretations. However, more newly created data is now available through a series expanding monitoring wells and pump tests 12 In order to unravel the movement and availability of Kerr County groundwater 50-years into the future we must first understand the "plumbing" of the subsurface and the surface A Groundwater Availability Model (GAM) requires a lot of -' data and interpretation. It displays and predicts how groundwater moves in the subsurface under differing conditions such as drought or newly drilled wells, even 50- years into the future. It might be viewed as a "what If" answer book. The first step is to get a good handle on the geology That requires drilling wells, logging wells and creating a series of cross-sections 13 Headwaters is performing all of the steps listed in the slide Headwaters is drilling approximately 3-monitoring wells per year entirely through all of the subsurface :~ aquifers. To date, we have drilled 7-monitoring wells Headwaters now monitors the water level from 22- wells each month including the 7-wells referred to above. 14 Kerr Co Digdal Elevation Map "". A Digital Elevation Model or DEM is one of the detailed maps that is incorporated into a GAM or Ground Water Availability Model The red areas represent the higher elevations moving down to lower elevations represented by the yellow,. green and the lowest blue areas The surface developed over the last 6.5 million years when the Texas Hill Country was uplifted and subsequently eroded into the present-day verdant hills and valleys This map is available at the the Headwaters office as a handout 15 Kerr County was occupied by very shallow Cretaceous seas from about 144-million years Before Present of about 95-million years Before Present The Llano Uplift was a large island that contributed a considerable amount of sand and gravel to the aquifers of Kerr County You could wade over most of the area during the deposition of the Cretaceous seas. This vast lagoon was flanked by series of barrier reefs extending from the Yucatan peninsula all the way around to the Carolinas. 16 The stratigraphy or layers of the Cretaceous seas are depicted above. Each layer is rock unit and it is not as tidy as depicted in this time- stratigraphic diagram as we will see in the next slide The yellow units are the aquifers The major confining units are the Upper Glen Rose and the Hammett clays. Water does not flow readily through the clay units The main producing units are Edwards, Lower Glen Rose, Hensel, Cow Creek and Hosston Minor amounts of ground water are found in the Upper Glen Rose and Sligo in isolated portions of the county ~~ This is a regional cross-section extending from Llano to Bandera. The previous time-stratigraphic diagram is applicable, but much more tidy than the physical reality J Note the massive yellow Hensel sand, which is the major recharge unit for all of the confined aquifers of Kerr County. The only unconfined aquifer in Kerr County is the Edwards limestone Kerr County is also underlain by the un-explored Ellenburger Group in isolated areas of the county. It is the main producing unit of Gillespie County 18 ~, Kerr Co Geology Map ' it #~ ~~ w~r hew' `. _ _.~ _. V./ ,, A detailed surface geology map is a necessary piece of knowledge that is blended into a GAM model B Note the area covered by the light blue colors These two shades depict the Edwards Group ~ The light and dark green colors are outcrops of the Upper and Lower Glen rose units The yellow shade represents alluvial or river borne material The surface geology depicts the Edwards a the higher elevations, while the green Glen Rose is at the lower elevations. 19 ~P ~•~ . '.• ~ ~ • •i1 •~ ,.~ Kerr Co Base Map Another critical step in building a model is the creation of a well data base Headwaters now has an interactive map of well J information that can be accessed with a click of a mouse This data base is now available and is being updated on a daily basis with a full time employee Note the TWDB well database, which is blended into additional local data and interpretation 20 Well logs are another piece of the puzzle that is part of building groundwater model Headwaters is building acounty-wide well index of aquifer and aquitard descriptions combined with geophysical logs Headwaters will run the samples on any deep well and geophysically log selected wells for private and public clients 21 Finally, after gathering the necessary information the model begins to be formed 22 Upon the completion of a model, the user is capable of asking what-if questions far into the future Many what-if questions may arise, such as if you drill twice as many wells into the Hensel in the Center Point area, what will happen to water levels 50-years from now? 23 The GAM models that has been set up for Kerr County contains a square mile grid covering 1,107 square miles or 708,480-acres which is 10-layers deep That translates to approximately 12,000 cells Data has to be placed within each individual cell. 24 As data is placed into the cells, contour maps can be constructed for each individual aquifer Data might consist of water levels for each individual ~ aquifer or the thickness of each individual aquifer on a square mile basis a Other maps may be constructed that represent various forms of data such as hydraulic conductivity, storage coefficients, and transmissivity 25 Each cell is one-square mile horizontally and various thickness in the 3rd dimension Since Kerr County changes its rock properties rapidly ~' across the county, it becomes a very complex array of rock geometry 26 This is an example of one column within the model depicting the conductivity of individual cells within the GAM The term "Conductivity" is only one of several characteristics of each individual cell. It essentially is a measure of how fast J or slow the water moves through the subsurface 27 The TWDB regional GAMs that overlap the Headwaters GAM are compared above It is evident that the Kerr Co model is much more complex than the TWDB models and contains a lot more detailed data 28 The GAM progress is reported in this slide Headwaters is now beginning to age date the groundwater from all of the aquifers This will allow calculations that will estimate the direction and speed of groundwater movement within the subsurface The isotope studies will also pinpoint the origin of the water and answer the question of recharge origin 2s In the course of the investigations several very important discoveries have been made Some of it is very good news and some of it is not so good news 30 Headwaters is actively communicating and cooperating with adjoining districts as well as state and federal agencies This presentation is an example of that communication and cooperation 31 Headwaters maintains an interactive Web site where a person can view the historic and latest water levels around the county Other links are provided for additional information such as news, rules and meetings If you could take the time to come to the office, you could view the information on the wells in the county on an interactive Arc GIS computer map You might also pick up handout cross-sections and maps Website : http://www.hgcd.org/ Phone: 830-896-4110 General Manger: Gene Williams 32 33 34