An Assessment of Direct Impacts to Wildlife Habitat from Future Water Development Projects. TPWD and USFWS 1990.

Executive Summary

This document lists projected direct impacts to wildlife resources from the future development of 44 reservoirs in Texas, outlines federal and state responsibilities concerning these impacts and provides preliminary data on land acquisition acreage necessary to achieve full habitat compensation for unavoidable losses to these wildlife resources. Impacts were determined from inventories of wildlife habitat and assessments of the overall quality of these habitats within planned reservoir locations. Information provided by this study generally does not represent the product of detailed analyses of potentially affected areas and is not intended to supplant detailed environmental studies on individual projects.

Assessment of impacts include:

  1. a description of dam site location;
  2. a listing of the specific types of wildlife habitat occurring within each reservoir site;
  3. acreage of these various habitats;
  4. habitat quality (suitability) ratings;
  5. projected habitat units lost;
  6. projected acreage necessary to fully compensate for the wildlife habitat lost;
  7. listings of State or Federally listed threatened or endangered species; and
  8. listings of occurring rare or unique plants, animals or natural communities.

Fish and wildlife resource impacts from reservoir construction also include the potential alteration of in stream flows and estuarine inflows. However, a quantitative analysis of these impacts was not within the capabilities or scope of this study.

While Texas currently has approximately 133 million acres of natural or semi-natural terrestrial wildlife habitat, much will continue to be degraded or destroyed by current land use practices including the development and operation of reservoirs. Forested river and creek floodplain vegetation including bottomland hardwoods, a particularly high value wildlife habitat, have declined from an estimated 16 million acres to 5.9 million acres. This represents a 63 percent loss with further prospects of additional losses to reservoir development, timber clearing and other land use changes.

Over 851,000 acres of wildlife habitat would be directly impacted by the 44 reservoirs. Almost one-third of this acreage includes bottomland hardwood forests, swamps and other important riparian vegetation.

Size of the reservoirs varies considerably from 118 acres to 99,500 acres. Those reservoirs creating the largest acreage impacts include Rockland, Tennessee Colony, Marvin Nichols I, Millican, Lindenau, Weches, Cuero, Bon Wier, Goliad and South Bend. Proposed reservoirs impacting wildlife habitats with the highest known quality include Lindenau, Weches, Cuero, Marvin Nichols I, Rockland, Clopton Crossing, Bosque, Bon Wier, Tehuacana, Goliad, Big Pine and Liberty Hill.

Increased public interest to develop environmentally acceptable water development projects has prompted close review of planned projects by both Federal and State regulating agencies. The process of determining the ultimate suitability of a project will require more extensive assessments of project needs, earlier identification and evaluation of potential impacts and enhanced coordination efforts among developers, resource agencies, political action groups and the general public.


This report documents projected direct impacts to wildlife resources from proposed future reservoir development in Texas and outlines State and Federal responsibilities concerning these impacts. Historically, neither immediate nor long-range water development planning has adequately addressed impacts to wildlife resources. Until recently, this was evidenced by failure to avoid losses, quantify losses, identify mitigating measures to reduce losses or finally, to include compensation for any losses which were unavoidable. These considerations remain controversial due to the concern of reservoir proponents to minimize project costs. Other factors which have contributed to the controversy include lack of knowledge or information concerning wildlife, the exhibition of insensitivity or even apathy for the impacted resources (particularly for bottomland hardwood forests, riparian systems and their associated wildlife) and lack of adequate coordination between governmental agencies. However, biological impact assessment and delineation of associated mitigative measures are now recognized as important phases of project development. These considerations have been significantly improved as a result of additional state and federal legislation, revised policies established by resource management agencies, increased activism by resource conservation groups and judgments resulting from litigation.

Results of previous involvement in planning and coordination between Federal and State resource agencies and water development interests indicate that early identification of losses or benefits to biological resources greatly assists the planning process. This identification allows the constructing agencies to incorporate such measures routinely with other project features, rather than having to later consider modifications to or deviations from original project plans. Further, early determination of biological resource impacts provides benefits to the resource management agencies by allowing them to identify projects which are particularly important in regard to resource losses and prioritize projects based on projected impacts. The process allows meaningful pre-development consultation prior to the submission of permit applications, enhances coordination efforts and increases the likelihood of obtaining successfully negotiated settlements.

The Texas Water Plan published in 1984 by the Texas Department of Water Resources identified 44 reservoirs from 65 potential sites for surface water development through the year 2030 to satisfy projected water supply needs. Data are presented concerning wildlife resource impacts associated with these 44 reservoir projects.

Findings of this report are intended to assist in advance planning and evaluation of these water development projects only from a broad, generalized perspective by providing data which illustrates projected impacts to wildlife habitat and compensation for loss of this habitat. Due to potential future land use changes and project design modifications, results are not intended to supplant detailed environmental studies to be conducted during the future planning stages of these projects. Similarly, compensation requirement figures do not represent specific mitigation recommendations of the Texas Parks and Wildlife Department or the Fish and Wildlife Service. Actual mitigation requirements will be determined according to these detailed studies and through coordination between the project developers, resource agencies and permitting authorities. The methodologies employed and results reported herein do not necessarily represent those most appropriate for use and consideration in detailed project assessments. Permits have been issued or are under consideration for several projects listed in the report. For these projects, special permit conditions or mitigation recommendations previously made to the permitting authorities have been noted.

While measurements of aquatic impacts relating to variations of instream flows and productivity of bays and estuaries are no less important than terrestrial studies, such investigations were beyond the scope of this report.

Interagency Planning and Coordination

Federal Responsibilities

The Fish and Wildlife Service (WFS) is an agency of the Department of the Interior, the Nation's principal conservation agency. The mission of FWS is to provide Federal leadership to conserve, protect and enhance fish and wildlife and their habitat for the continuing benefit of the people (FWS 1980a). Mandates for FWS activities to conserve fish and wildlife resources are contained and interrelated in numerous Federal laws including the National Environment Policy Act (NEPA), Clean Water Act, Migratory Bird Treaty Act, Endangered Species Act, and Fish and Wildlife Coordination Act.
The basic authority and responsibility for FWS involvement in habitat mitigation planning on reservoir projects comes from the Fish and Wildlife Coordination Act of 1958 (FWCA). The FWCA can be highlighted as follows:

  1. Authorizes FWS to investigate and report on Federal water development projects and non-Federal actions requiring a Federal permit or license.
  2. Specifies that fish and wildlife conservation shall receive equal consideration with other project purposes.
  3. Requires that a Federal agency consult with FWS and the State fish and wildlife agency concerning the effects on fish and wildlife resources of a Federal water resource development project or non-Federal water development project requiring a permit or license.
  4. Federal agencies authorized to construct or operate water resource projects [primarily the Corps of Engineers (CE) and Bureau of Reclamation (BR)] or approve permits and licenses for non-Federal projects [primarily the CE and Federal Energy Regulatory Commission], are required to give full consideration to the report and recommendations of the Secretary of the Interior, represented by the FWS.

In an effort to assure consistent recommendations, balanced multiple use of natural resources, reduce delays and conflicts and allow development interests to anticipate recommendations, the FWS has developed a Mitigation Policy (FWS 1981a). The policy is based on the principles of avoidance and/or compensation for the most valued fish and wildlife resources. A more complete discussion of the FWS Mitigation Policy and its resource categories is contained in a later section of this report.

In Federal water project studies by agencies such as CE and BR, FWS is a member of the environmental planning team for project studies. The FWS operates under National memoranda of agreement with those agencies to provide fish and wildlife resource planning input including mitigation and enhancement recommendation. Funds for expenses of this planning input are provided to FWS under regional agreements. Section 2 of the FWCA also requires Federal water development agencies to include FWS reports on fish and wildlife resources in submissions to Congress for project authorities.

Section 404 of the Clean Water Act regulates virtually all water development projects, and therefore, is the primary mechanism for FWS input on most non-Federal reservoir projects. The Corps of Engineers (CE) operates the regulatory permit program to implement Section 404. Through a public notice and open comment period process, the CE receives input on all aspects of reservoir projects. Specific input on fish and wildlife resource impacts is received from the FWS and the Texas Parks and Wildlife Department (TPWD).

With most reservoir projects, an Environmental Impact Statement is also prepared by CE to meet requirements of NEPA. For these projects the total processing and interagency planning period may exceed six months. Early coordination (pre-application) by water development interests can greatly expedite the processing of permit actions and attendant environmental documents. This early coordination allows evaluating entities like FWS and TPWD ample time to schedule and complete joint field studies such as habitat evaluations.

In addition to the evaluation of terrestrial habitat impacts from reservoir construction, FWS also evaluates impacts on the aquatic resources. This frequently includes the potentially disrupted stream fishery systems and downstream estuary systems which may suffer altered inflows as a result of reservoir construction. The cooperative evaluation of these aquatic impacts with TPWD and the National Marine Fisheries Service (NMFS) is another key FWS responsibility. However, the time-intensive requirements of existing methodologies to assess these impacts are too excessive to include in this preliminary assessment of reservoir projects.

Since the 1985 modifications to the Texas Water Code and the parks and Wildlife Code, FWS has been cooperating with TPWD to assess habitat impacts during the State water permit process of reservoir planning. In the normal routine a Texas Water Commission (TWC) permit is granted prior to Federal Section 404 permit processing. Coordinated assessment and recommendations at this first permit stage could virtually eliminate the need for re-assessment during Federal permit processing.

The FWS is improving its ability to address fish and wildlife problems and needs and to provide input, with TPWD, to Federal and State regulatory entities for reservoir projects. The agency will continue to develop state-of-the-art methodologies, provide objective and complete answers to resource questions, and to discharge public trust responsibilities.

State Responsibilities

Actions by the 69th Texas Legislature and passage of constitutional amendments in November 1985 resulted in modifications to the Texas Water Code and Texas Parks and Wildlife Code.

The changes effectively increased responsibilities of the Texas Water Commission (TWC) and the Texas Parks and Wildlife Department (TPWD) in considering fish and wildlife resources in the water permit process. New mandates included increased emphasis in determining the effects water development will have on fish and wildlife resources, and greater interaction between State and Federal agencies involving advance planning and the permit application review process. Specific sections of the 1985 additions to the Codes are summarized below:

Texas Parks and Wildlife Code

Section 12.0011. Resource Protection. TPWD is the State agency with primary responsibility for protecting the State's fish and wildlife resources. TPWD's Resource Protection activities include:

  1. investigating fish kills;
  2. providing recommendations that will protect fish and wildlife resources to local, State, and Federal agencies that approve, permit, license or construct development projects;
  3. providing information on fish and wildlife resources to any local, State, and Federal agencies or private organizations that make decisions affecting those resources; and
  4. providing recommendations to TWC on scheduling of in-stream flows and fresh water inflows to Texas estuaries for management of fish and wildlife resources.

Section 12.024. Water Permit Responsibilities. Important conditions of this section include:

  1. The TWC shall furnish to the TPWD a copy of all permit applications to store, take, or divert water.
  2. The TPWD shall make recommendations to protect fish and wildlife resources, including permit conditions, mitigation, and schedules of flow or releases.
  3. The TPWD shall be, on its request, a full party in any hearing on an application for a permit to store, take or divert water.

In addition to the Texas Parks and Wildlife Code, TPWD actions are further guided by policies and directives established by its nine member Commission. It is the policy of the Texas Parks and Wildlife Commission to seek full mitigation for fish and wildlife losses occurring as a result of water resources development projects.

Texas Water Code

Constitutional amendments passed in 1985 promoted several important amended changes to the Texas Water Code involving fish and wildlife considerations and reservoir development.

Section 11.147. Effects of Permit in Bays and Estuaries and Instream Uses. In its consideration of an application to store, take, or divert water, the Texas Water Commission (TWC) shall consider the effect, if any, of the issuance of the permit on fish and wildlife habitats. The TWC must send a copy of the permit application with any amendments to TPWD for review. After review of the application TPWD would have the option of becoming a party to any of the permit application hearings. In formulating a decision TWC must consider, in addition to other information, all evidence or testimony presented by TPWD or TWC staff.

Section 11.149. Effects of Permits on Fish and Wildlife Habitats. In its consideration of an application for a permit to store, take, or divert water in excess of 5,000 acre feet per year, the TWC shall assess the effects, if any on the issuance of the permit on fish and wildlife habitats and may require the applicant to take reasonable actions to mitigate adverse impacts on such habitat. In determining whether to require an applicant to mitigate adverse impacts on a habitat, the TWC may consider any net benefit to the habitat produced by the project. The TWC shall offset against any mitigation required by the U.S. Fish and Wildlife Service pursuant to 33 C.F.R. Sections 320-330 any mitigation authorized by this section.

The term "habitat" as mentioned in Section 11.149 refers to either terrestrial or aquatic systems which would be destroyed, altered, or otherwise impacted. In the process of evaluating biological impacts of a proposed reservoir, gains and losses to aquatic and terrestrial components are evaluated separately due to disparate biological characteristics of these systems. Mitigation recommendations provided to the TWC by TPWD will maintain this differentiation and not attempt to balance terrestrial losses with aquatic gains or vice versa.

Section 15.3041. This section appropriates five percent of the annual firm yield of any reservoir and associated works with state financial participation within 200 river miles from the coast to TPWD for releases to bays and estuaries and other instream uses. Memoranda of understanding are being established with TWC and the Texas Water Development Board as required by Section 15.3041 to provide procedures for release and management of the water and for additional research in determining bay and estuary instream flow needs.

Participation by TPWD in the water permit process will be in cooperation with Federal agencies including the FWS and National Marine Fisheries Service to enhance information exchanges and ensure compatibility with the Federal permitting process.

Importance of Early Consultation

As a result of the new legislative revisions to the Water Code and parks and Wildlife Code, five opportunities are presented at which fish and wildlife considerations may be addressed during the planning and development of a reservoir (McKinney and Rieff 1987). These include: pre-application consultation, State permit (water right) process, post-application consultation, Federal permit (404/10) process, and litigation.

Histories of several recent reservoir projects have indicated that without early consultation, planning and development were deficient enough to delay State and Federal permit issuance and even trigger litigation. Such events could significantly set back construction dates, prompt significant project modifications or in extreme situations, stop the project indefinitely.

Early consultation and planning will provide much greater opportunity to incorporate considerations for fish and wildlife resources in project development, which may eliminate or minimize cost efficiency and enhance overall development efforts.


Current Status of Wildlife Habitat in Texas

Vegetation (habitat) inventory data were derived from maps produced by the Texas Parks and Wildlife Department (TPWD) as part of a statewide vegetation mapping effort completed in 1981. Vegetation was categorized using both digital data and imagery obtained from the Landsat satellite system during the years 1972 through 1980. Classification analyses were performed using a computer-assisted supervised approach which was later modified to incorporate a multi-temporal analysis capability. This allowed classification of ground cover using data from two or more seasons. Classification accuracies using this methodology generally exceeded 90 percent. TPWD's mainframe computer system was utilized in association with a Comtal 3060 Series digital Image Display System during the course of the classification analyses. A computer compatible classification tape was produced from which data could be further processed into two principal products for each Landsat scene:

  1. a classification map portraying major vegetation associations, and
  2. a quantitative inventory giving the acreage of each vegetation association occurring with each scene.

Delineation of the vegetation classes was guided statewide by using a standardized plant association nomenclature. Each association name was listed according to floristics that signified dominant plant species and a physiognomic structure which addressed height and canopy coverage of the occurring types.

Inventory data were stored on computer compatible tapes for 23 published maps of Landsat scenes representing the eastern two-thirds of Texas. Acreage data were also generated for the western one-third and panhandle regions of the State using a combination of Landsat imagery and other information provided by the Bureau of Economic Geology, University of Texas, Austin (Kier et al. 1977). Descriptions of the methods and procedures used to produce the statewide vegetation maps and associated quantitative inventory information are detailed by TPWD (1978, 1980, 1981).

Inventory of Cover Types within Proposed Reservoir Sites

Vegetation inventory data derived from previous evaluation studies by the Fish and Wildlife Service (FWS) were used to assess 15 of the 44 reservoir sites. Cover type information for these projects was normally obtained through conventional photo-interpretation methods. For the remaining reservoir sites, inventory information was generated from Landsat data through combined effort of TPWD, Texas Natural Resources Information System (TNRIS), Texas Water Development Board (TWDB), and the Texas Water Commission (TWC).

Landsat inventory data classified and stored on digital tapes by TPWD were transferred to TNRIS. Control point data listing both satellite coordinates and corresponding latitude-longitude coordinates were provided for each Landsat scene. Base maps at a scale of 1:24,000 were prepared from reservoir location information provided by the TWDB which included specified dam site locations and planned normal operating or conservation pool elevations. After delineation of the reservoir boundaries, the base maps were digitized using TWC's "Bendix Data Grid" digitizer. The digitized latitude-longitude coordinates were converted into satellite scanner coordinates using the control point data and rectification equations. This digitizing process allowed the generation of inventory printouts for each reservoir site including all occurring cover types within the scene, acreage of each occurring type, and total area digitized. A visual portrayal of the juxtaposition and arrangement of the cover types within each reservoir site was also produced using a "Ramtek Color Graphics System" Model 93-51RM digital image display system provided by TNRIS. The vegetation cover maps for reservoirs illustrated in this report were generated from this system.

A variety of structural and vegetation type classification systems have been used to describe cover types (habitats) in previous reservoir impact studies. For example, a site might variously be described as a deciduous forested wetland, a willow oak/elm forest or a bottomland hardwood forest by different biologists studying the same area. In order to simplify comparison of reservoir sites the cover types listed in the reservoir data section of this report have been standardized. They generally conform to the physiognomic class descriptions listed in the Appendix.

Evaluation of Wildlife Habitat Quality for Impacted Sites

Two methods were used to evaluate the 44 reservoir sites. The Habitat Evaluation Procedure (HEP) developed and implemented by the FWS (1980b) was used for 14 reservoirs which had been evaluated as a result of previous planning work. No previous studies were available for the remaining 30 sites. For these reservoirs, the Wildlife Habitat Appraisal Procedure (WHAP) developed by TPWD was used (Frye 1986). Both procedures evaluate wildlife habitat rather than wildlife abundance as direct population measurements are nor feasible or practical due to the generally reclusive nature of most wildlife species. These approaches assume that vegetative structure, including species composition and physiognomy, is itself sufficient to define the habitat suitability for wildlife.

The HEP method is based on measuring habitat components which are requisite to the health and well being of selected wildlife species which would commonly occur within a particular habitat type. Life requisites include food, water, cover, reproductive, or special requirements supplied by the habitat. These components are measured for selected species to determine the potential of the area to support the species. This habitat suitability is measured by an index number bounded by 0.0 and 1.0 where 0.0 represents unsuitable habitat and 1.0 represents optimal habitat. This habitat suitability index (HSI) when multiplied by the number of acres of the habitat (or vegetation cover type) gives a numerical value known as a habitat unit (HU). The HU provides a standardized basis for comparing habitat changes both temporally and spatially and is also used to calculate compensation (full replacement requirements) for induced losses.

The WHAP measures key components of each cover type which contribute to ecological condition of the cover type and resulting overall suitability for wildlife. The WHAP was designed to obtain a direct measure of the habitat suitability for wildlife using an assessment of ecological productivity and diversity rather than an evaluation based on the selection of individual wildlife species. Key habitat components which are evaluated include: site potential for woody and herbaceous plant production; age of existing vegetation; relative abundance of the habitat type and its value to wildlife; diversity of occurring woody species; vertical stratification of vegetation canopy cover; relative abundance or the scarcity of dens and refuge sites; and availability of browse and herbaceous material. A habitat quality (HQ) score was derived from this evaluation for each cover type. The use of this value is identical to the habitat suitability index (HSI) employed by the HEP. Habitat Units (HU's) are derived by multiplying the average habitat quality score (HQ or HSI) of the cover type by the number of acres of the occurring cover type. Mathematical application and use of the HU values for evaluating project impacts is identical to the HEP process.

To further standardize the HEP and WHAP evaluations for the purposes of this document, HSI values obtained for particular wildlife species on previously conducted HEP evaluations were averaged for all the species occupying each cover type to provide numerical values compatible with WHAP.

For those 30 reservoir sites where the WHAP methodology was applied, cover types occurring within a reservoir site were sampled according to the following procedures. Occurring cover types, corresponding acreage of each type and the percent of the total reservoir area comprising each type were determined as previously described. With the exception of swamps, bottomland hardwoods and other riparian woodlands, any cover type which comprised less than 10 percent of the total area within any reservoir site was grouped into an "other" category and not evaluated.

At least two evaluation sites were selected for each cover type with coverage greater than or equal to 10 percent of the total reservoir area. For most reservoirs, at least three sites were selected for swamps, bottomland hardwoods and other riparian cover types.

Selection of site locations, although stratified to include different areas within the reservoir sites, was influenced by the availability of public road access. When necessary, permission was obtained to access suitable sites on private property. Each site was visited by a minimum of two investigators including at least one representative each from the FWS and TPWD.

Determining of Resource Categories with the FWS Mitigation Policy

Under the guidelines of the FWS Mitigation Policy (FWS 1981a), the degree of mitigation required for development impacts to fish and wildlife resources depends on the resource category determination. Resource categories are based on the value (importance) and scarcity of habitat to evaluation species, populations or communities representing ecological, social or economic aspects of the habitat. The resource categories and mitigation planning goals in the Mitigation Policy are summarized in Table 1. The basis for determining the status of existing habitat values and potential impacts of development on that habitat value is normally HEP or other habitat based methodology, such as WHAP. In-kind habitat values referred to in Table 1 generally mean value of the same habitat type. Existing habitat values mean habitat values at the specific site in question.

Table 2 is intended to clarify the policy and implementation strategies by hypothetical example. The intended effect of the Mitigation Policy and resource category determinations is the avoidance or compensation of impacts to the most values resources and the formulation of mitigation recommendations that correspond to the value and scarcity of the habitat at risk.

The actual resource category designation should be made through consultation between FWS and TPWD, as well as other resource agencies such as the Environmental Protection Agency (EPA) or National Marine Fisheries Service (NMFS) whenever resources of concern to those agencies are involved. These determinations should be made as early as possible in the planning process by accessing each habitat with regard to the designation criteria. The Mitigation Policy also suggests that certain FWS priority habitats and special aquatic and terrestrial sites, including designated wildlife areas, be given special consideration as either resource category 1 or 2.

Although the resource category determinations displayed for WHAP evaluations in this document are based on considerable experience with other designations in the State and consultation with local expertise when it was available, they should be considered preliminary. Most of the determinations for HEP evaluation sites are direct reference from FWS planning documents.

Table 1. Resource categories and mitigation planning goals
Resource Category Designation Criteria Mitigation Planning Goal
1 High value for evaluation species and unique and irreplaceab.e No loss of existing habitat value
2 High value for evaluation species and scarce or becoming scarce No net loss of in-kind habitat value
3 High to medium value for evaluation species and abundant No net loss of habitat while minimizing loss of in-kind habitat value
4 Medium to low value for evaluation species Minimize loss of habitat value

Table 2. Hypothetical examples of mitigation policy implementation
Resource Category Habitat Site Mitigation Policy Implementation
1 Unique wetland marsh in desert No loss of habitat unit (HU) value at site
2 Bottomland hardwood (bh) forest Any loss of HU value must be fully compensated in kind with equal HU
3 Brushland habitat Any loff of HU must be fully compensated (can be from other Hu's)
4 Bermuda grass pasture Loss of HU value should be replaced when practical (can be with any HU type)

Calculation of Compensation Requirements

Mitigation is defined as any action taken to lessen the adverse impact of a construction project on wildlife resources. In the pursuit of water development planning, the most preferred project alternatives would be those which completely avoid any adverse impacts to the wildlife resources. For those projects mitigation would not be necessary. Unfortunately, the geographical location of reservoir sites within river floodplains and major creek drainages usually creates significant impacts to wildlife by inundating higher quality habitats including bottomland hardwoods and associated riparian vegetation. Under these circumstances one or more of the following mitigation measures would be applicable: 1) minimizing the impacts by changing the project location, design, or operational plan; 2) rectifying the impact by repairing or rehabilitating the affected environment; 3) reducing or eliminating the impact over time; and 4) compensating for any net wildlife losses created as a result of the impacts. These mitigation alternatives were standardized in the National Environmental Policy Act regulations on procedures in 1978 (President's Council on Environmental Quality 1978). While the first three measures apply to reducing net losses, the latter provides a means for replacing resource losses that cannot be minimized or avoided.

The concept of compensation is based on the principle that wildlife resources are renewable and thus can be replenished through acquisition and management of suitable land. Habitat impacts and compensation credit are quantified using habitat units (HU's). Habitat units are calculated by multiplying habitat quality (HQ or HSI) by habitat quantity (acres).

An area of land has an existing inherent value. To receive compensation credit for an area, the land must be managed to increase its carrying capacity (as measured by HQ) so it can maintain existing wildlife populations while concurrently supporting additional population to make up for the wildlife lost as a result of the project impacts. Management may be through physical changes to improve the habitat or passive protection form disturbances, thus allowing natural succession. In either case, to obtain gains in habitat value for compensation from an acre of habitat, that acre must be managed to increase its existing habitat quality.

The formula for determining acreage requirements to compensate for project losses is derives as follows:

For example, if 10 acres of wildlife habitat quality value of 0.6 were inundated, a total of 6 HU's would be lost [10 (acres) x 0.6 (HQ) = 6 (HU's)]. If another 10 acres with an existing HQ of 0.6 were acquired, no compensation credit would be given because there was no increase in habitat value over existing conditions. However, if the existing habitat with an HQ value of 0.6 was immediately increased by 0.4 to its maximum value of 1.0, then 15 acres would fully compensate [6 (HU's lost) / 0.4 (HQ increase) = 60 (compensation acres)]. These examples illustrate that compensation acreage requirements cam become significantly higher as the potential gain in habitat quality decreases.

There is a fallacy in always relying on the premise that poorer quality (low HQ or HSI) compensation lands are preferred for reservoir mitigation planning. Although less acreage may theoretically be required to compensate for losses, the management costs to realize the desired gain in HU's is often prohibitively expensive on these lands. Generally, it is most economically efficient to seek lands of moderate habitat value (or high habitat value where protection is needed) for compensation. The expected future condition of the compensation lands in question may be a major factor in determining actual compensation requirements. If important compensation area habitat is being disrupted by other factors such as unregulated development, the HU losses prevented by protecting the area can be credited to the mitigation plan.

Reservoir site planning should include avoidance of large acreage of cover types exhibiting high habitat quality such as bottomland hardwoods which leave little room for habitat improvement. Compensation requirements for this type of habitat may be quite high. Conversely, cover types exhibiting low habitat quality require less acreage for full compensation of losses. Additional information is available concerning these principles, the above formula and the determination of compensation requirements (Corps of Engineers 1980), (FWS 1980b).

Each of the 44 reservoir projects was evaluated to determine the acreage requirements necessary to fully compensate for the projected losses. Due to the preliminary nature of project design data for most of the reservoirs, no projections were made concerning development schedules and associated delayed gains or losses in habitat value arising from future changes to either quantity or quality of existing cover types, and no candidate mitigation sites were evaluated. To standardize the evaluations and make results comparable the following assumptions and conditions were established:

  1. All reservoir impacts to terrestrial habitats result in instantaneous loss of habitat value within specified conservation pool or normal operating pool areas.
  2. Hypothetical compensation sites would have the same baseline and future without a project HQ's as the impact areas, with a maximum potential HQ of 1.0 for each occurring cover type. Management of compensation areas would result in an instantaneous gain in habitat value. In reality these conditions rarely occur and the overall effect of these assumptions is to somewhat reduce or moderate the compensation acreage requirement.
  3. Impacts were projected only for land subject to permanent or semi-permanent inundation. Projections were made for only those cover types comprising 10% or more of the total area to be inundated (except for bottomland hardwoods, riparian woodlands, and swamps which were included regardless of size). This procedure also tended to reduce the overall calculated compensation acreage requirements for many sites.

Compensation requirements for each of the impacted cover types were calculated according to three hypothetical values representing proportional amounts (25%, 50%, and 100%) of the total potential HQ gain which could be obtained with management. Raising the potential gain in habitat quality of a compensation area by 25% assumes relatively minimal management; an increase of 50% assumes moderate management; while achieving 100% of the potential gain assumes intensive management. Minimal management could include marking wildlife management area boundaries, providing protection by periodic surveillance, limited grazing control and allowing the habitat quality to increase through natural succession. Moderate management might include the above measures with the addition of some selected herbaceous seedings and limited vegetation manipulation through controlled burning, discing, thinning or other means. Intensive management could include significant efforts to reestablish specific species of grasses, forbs, woody shrubs or trees through supplemental plantings and vegetation maintenance. Establishing indices of relative abundance of wildlife species and conducting research associated with specific wildlife needs could also be included. Both moderate and intensive levels of management could also include wildlife trapping, transplanting or restocking efforts. All three levels of management would likely include wildlife-oriented public recreational use. The actual time, effort and significant habitat improvement may be major in some instances, particularly when reestablishment of slow maturing vegetation species is required.

It should be reemphasized that the calculation of compensation requirements for projects evaluated by this study may not be the same as mitigation recommendations in previous reports or future site specific evaluations. A number of factors which can influence these differences include standardized project assumptions for this study, variations in project design, land use changes and projections, and the priorities for certain habitat types. The compensation requirements displayed in the Reservoir Data section of this report are intended to provide preliminary data in a format where each reservoir site can be compared.

Assessment of Significant Flora and Fauna

Potential occurrence of endangered, threatened, or unique flora and fauna was investigated for each of the reservoir sites by referencing TPWD databases. Information on TPWD listed animal species was supplied by the Non-game and Endangered Species Program. Possible, probable or confirmed occurrence of particular species by reservoir site is given. This information was obtained by consolidation of county lists for those counties represented within a particular reservoir location. Federally listed species are also indicated in the summary section.

Information on unique plants, animals, and natural communities was provided by the Texas Natural Heritage Program (TNHP). The TNHP database system was established to increase public awareness of the natural diversity of Texas and to facilitate its preservation. The information system is continually maintained and updated with site specific information on the occurrences of rare plants and animals throughout Texas. The best examples of natural communities are also tracked with this system.

Base maps indicating proposed reservoir boundaries and/or 7.5 minute topographic maps representing the proposed reservoir location were provided to the TNHP staff. Queries were made to the information system from which output was obtained providing descriptive information for those occurrences on record.

The TNHP information included here is based on the best data available to the State regarding threatened, endangered, or otherwise sensitive species at the time of this review. However, the data do not provide a definite statement as to the presence or absence of special species or natural communities within a proposed project area, nor does it substitute for an evaluation by qualified biologists. It is intended to assist in the assessment of these proposed sites to avoid harm to sensitive species and natural communities.

Results and Discussion

Current Status of Wildlife Habitat in Texas

Statewide Inventory

The statewide vegetation inventory completed by TPWD using Landsat data through 1980 indicated that Texas has about 133 million acres of wildlife habitat remaining. This can be further subdivided into eight physiognomic categories: grasses (32%), brush (20%), shrub (15%), parks (13%), forest (13%), woods (6%), swamps ( <1%), and marsh (<1%). Criteria for designation of these categories is listed in the Appendix. Among these categories a total of 78 plant associations were inventoried, mapped, and later consolidated into 46 major cover types (McMahan et al. 1984). Crops, water and urban/sparsely vegetated lands were also included.

Although the amount of wildlife habitat acreage occurring throughout Texas is presently significant, most is being altered adversely through continued land use conversions and emphasis on agricultural and forestry production. Most grassland associations, while comprising the largest category in total acreage, are considered to be among the lowest quality of wildlife habitats due to severe limitations in providing the necessary life requisites such as woody cover and plant diversity for many species of wildlife. While native, climax prairies and savannah associations often provide excellent habitat for some wildlife species they are extremely rare and have largely been replaced by tame pastures and overgrazed disclimax associations. Although approximately 35% of the total native habitat is composed of woody shrub and brush species, many of these species are considered "noxious" by agriculturists and are exposed to continuing pressure for intensive control and ultimate reduction. Parks, woods and forests together comprise almost one-third of the remaining native habitat but are also being reduced or altered in many areas through conversion to pasture, agricultural land or timber production. Included in this category are bottomland hardwood forests which are among the highest quality and most productive wildlife habitats in Texas.

Bottomland Hardwood Forests & Forested Riparian Vegetation

The amount of forested floodplain vegetation including bottomland hardwoods occurring prior to the settlement of Texas is estimated at 16 million acres. This estimate is based on acreage of occurring geologic floodplains in Texas (Kier et al. 1977) and assumes that all or most of these floodplains were originally forested. Remaining forested vegetation (excluding swamps) inventoried by Landsat was 5,973,000 acres in 1980 indicating a 63% loss of the original flood plain component. This remaining bottomland acreage would superficially appear significant, but actually constitutes only three percent of the total land area in the state and comprises just seven percent of all occurring woody vegetation. A geographical distribution of the remaining acreage of bottomland hardwoods in Texas is given in Table 3. Although forested riparian habitats west of the Navasota River are no less important than those in the eastern sections of Texas, they are not generally referred to as "bottomland hardwoods" by most biologists. For this reason those habitats are separated in Table 3 and called "riparian forests or woods" in this report.

The continued decline of high quality bottomland hardwood forests and associated wildlife has prompted preservation efforts by a number of entities. A program to preserve bottomland hardwood habitat and associated wildlife resources in Texas has been initiated by the FWS. Specifics of this program including goals and objectives, descriptions of biological resources and identification of 62 candidate preservation sites have been documented by the FWS (1984a). Each of the 62 identified hardwood bottomland sites was prioritized according to habitat quality and overall value to waterfowl, principally wood ducks (Aix sponsa) and mallards (Anas platyrbynchos). Areas ranking high for these species would similarly rank high for many other wildlife species. Among these 62 candidate sites, 19 lie within the boundaries of reservoirs listed herein, while proposed reservoir locations conflict with seven of the top 14 "priority 1" preservation areas. These potential conflicts are noted in the appropriate reservoir data sections. Information also includes FWS site priorities defined as follows:

TPWD is also pursuing bottomland hardwood preservation largely through coordinated mitigation planning with the FWS and direct acquisition of waterfowl habitat using funds derived from the sale of Texas waterfowl stamps and prints.

Proposed Reservoirs

The Texas Water Plan (TDWR 1984) identifies 44 reservoirs proposed for development through the year 2030 to satisfy projected future water needs in Texas. Names of the reservoirs with suggested dates of construction are given in Table 4. Sixteen reservoirs have been listed for development through 1989, 12 are planned during the 1990's, with 16 scheduled between the years 2000-2030. The location of these reservoirs is provided on Plate 1.

Reservoir Data

This section contains summarized tabular information for each of the 44 reservoirs. Data includes general location, proposed normal operating or conservation pool elevation, type of field evaluation conducted, and date of evaluation. Dam site information is given according to distance from nearest towns, bridge crossings or in association with actual river mile (RM) locations. The numerical value representing the appropriate resource category as discussed is given in parentheses after each cover type. Compensation requirements are calculated for each of the major cover types by dividing the Habitat Units (HU's) lost by the potential habitat quality (HQ) gain to be achieved through management of the compensation area. Calculations were performed for each of the cover types based on three hypothetical management option: minimal management which achieves 25% of the potential maximum gain; moderate management which achieves 50% of potential maximum gain; and intensive management which achieves 100% of the potential maximum gain. Numerical values for the potential HQ gain and associated required compensation were not rounded to facilitate calculation derivation and tracking.

Compensation values are summed for all of the cover types providing total estimates for each reservoir site according to each level of management effort. This method of information portrayal was modified for Cooper and Stacy Reservoirs which were under construction during preparation of this report. A summary of the 1981 mitigation settlement is provided for Cooper Reservoir, while the terrestrial wildlife mitigation conditions included in the 1987 section 404 permit are provided for Stacy Reservoir.

Information is also provided concerning the potential county occurrence or status of particularly important flora or fauna as determined by TPWD or specific local occurrence recorded in TNHP databases. Please note asterisks for the TPWD listed species and the following corresponding explanations:

Table 3. Geographical distribution of bottomland hardwood and other forested riparian vegetation in Texas – 1980
Location Amount (acres) Subtotal
Trinity River 305,000  
Neches River 257,700  
Sabine River 255,000  
Sulphur River 175,000  
Cypress Bayou 89,000  
Angelina River 88,000 1,169,000
Other Streams, Rivers, Creeks, Riparian Drainages east of the Navasota River   3,062,000
Remaining Streams, Rivers, Creeks, Riparian Drainages including and west of the Navasota River   1,742,000
Total   5,973,000

Table 4. Reservoirs identified for development through the year 2030 (TDWR 1984)
Reservoir Date Reservoir Date
1. Cooper 1987-1988 23. Millican 1994-1995
2. Upper Guadalupe 1987-1988 24. Prairie Creek 1994-1995
3. Stacy 1987-1988 25. Bedias 1996-1997
4. Applewhite 1987-1988 26. Cleveland 1996-1997
5. Wallisville 1987-1988 27. Colorado Coastal Plains (Shaw's Bend) 1996-1997
6. Retamal 1987-1988 28. Liberty Hill 1998-1999
7. Rio Grande Channel Dam A 1987-1988 29. Lake Creek 2000-2001
8. Paluxy 1987-1988 30. Lockhart 2002-2003
9. Justiceburg 1987-1988 31. Little Cypress 2002-2003
10. Eastex 1987-1988 32. Tehuacana 2004-2005
11. Palo Duro 1987-1988 33. George Parkhouse I 2004-2005
12. Big Sandy 1988-1989 34. Rockland 2004-2005
13. Big Pine 1988-1989 35. Weches 2010-2019
14. Sweetwater Creek 1988-1989 36. Cureo 2010-2019
15. Bosque 1988-1989 37. Cibolo 2010-1019
16. Post 1988-1989 38. Breckenridge 2010-2019
17. South Fork 1990-1991 39. Goliad 2010-2019
18. Lindenau 1990-1991 40. George Parkhouse II 2010-2019
19. South Bend 1990-1991 41. Bon Weir 20 in this file.
20. Caldwell 1990-1991 42. Carl Estes 2020-2030
21. Ringgold 1994-1995 43. Tennessee Colony 2020-2030
22. Clopton Crossing 1994-1995 44. Marvin Nichold I 2020-2030

Proposed Reservoirs

Proposed Reservoirs in Texas

Reservoir Data

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