trip report alamosa and monte vista national wildlife refuges

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Trip report Alamosa and Monte Vista National Wildlife Refuges

4-5 August 1991

Monte Vista NWR 4 August 1991

In attendance:

Steve Berlinger, Refuge manager Leigh Fredrickson, Gaylord Lab

Overview:

Monte Vista and Alamosa refuges are located in the San Luis Valley in southern Colorado. Elevation is around 7,600 feet, and the Rio Grande River runs through the valley. Originally Monte Vista had a flowing spring and an excellent trout fishery. Artesian water was abundant in the basin. The Valley has 2 aquifers. One aquifer is confined deep below a clay layer at a depth of 1500 to 3000 feet. Water temperature is 85°F. This warm water is used to raise alligators and tilapia. Monte Vista refuge is in a western portion of the valley, an area that has been highly disturbed by agriculture. Areas to the west, northwest, east and southeast of the refuge are in more natural-like conditions. Irrigation drains run through the Monte Vista Refuge. Water quality of drain water is poor because of the presence of heavy metals and pesticides. Thus, the refuge no longer uses drain water directly from the channel. This drain also has an impact on water level management in adjacent impoundments. Impoundments immediately adjacent to the drain are more difficult to flood and more difficult to keep flooded.

MONTE VISTA NATIONAL WILDLIFE REFUGE

Monte Vista Refuge has a primary goal of providing breeding habitat. The refuge normally produces over 20,000 ducks, most of which are mallards. Other waterfowl include cinnamon teal, blue-winged teal, pintail, gadwall and redhead. Other waterbirds are avocet, ibis, blackcrowned night-heron, American bittern, and shorebirds. The refuge also is an important migration stopover for sandhill and whooping cranes. Ducks peak at 40,000 and raptors are abundant.

Use of water (ditch and well) is tremendous with about 20,000 acre-feet used annually. Pumping cost reach $70,000. At times when pumps are used on the refuge, several artesian wells stop flowing. In some cases water that is pumped returns to the ground water immediately because continuous pumping is r ·equired to maintain water levels. Berlinger had the irrigation district circulate water through the irrigation supply ditches during winter. Because the flow never reaches the Rio Grande River it is assumed that this irrigation water is recharging the water table.

Cattail and bulrush are common robust marsh plants. Greasewood areas that were converted to nesting habitats are now dominated by Baltic rush. Two problem plants are Canada thistle and whitetop (Lodium

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MONTE VISTA AND ALAMOSA NATIONAL WILDLIFE REFUGES 2

sp.) Whitetop can be reduced with grazing or by herbicide application. The refuge has aerial sprayed to control the problem for years. One unit is choked with filamentous algae. The algae is particularly dense away from the well site. The unit is along the east side of Refuge Unit 24.

For best use as waterfowl nesting habitat, a heavy thatch and water flowing under the Baltic rush is necessary. Predation is high and is primarily from skunks and ravens. Nests in Baltic rush are very visible to an aerial predator. Greasewood has been largely eliminated because of changes in hydrology.

Currently, two colonial waterbird colonies are established on the refuge. The goal is to develop 3 colonies. By increasing the number of colonies to 3, there will be greater options to switch vegetation management among units via drawdowns and other manipulations among units without having a detrimental impact on the total number of marsh nesting birds on the refuge.

Other management, problems, and wildlife:

Many powerlines cross the refuge. An auto tour route was historically 6 miles in length but has been reduced to 3 miles. The hunting program is excellent.

Weed board and extension people are concerned about thistle and whitetop.

Dormant season grazing has been used consistently but drawdown strategies have not.

There has been a long-term waterfowl production study based on 167 miles of transects that are walked twice annually. These data largely are related to the effects of grazing on duck nesting. How were changes in wetland conditions and productivity over the past 20 to 30 years incorporated into the study?

Made a loop west of Colorado Route 15 towards the west boundary of the refuge. Saw 8 antelope, one of which was a very large buck. No elk, but about 500 winter on the area. About 12 or so are spending time on the refuge this summer. One problem with ungulates is mortality associated with woven wire fences. Some of these woven wire fences have been replaced with a single hot wire to reduce mortality. Past refuge policy was to keep elk off refuge because of competition for waterfowl food crops.

Moist-soil

A unit (Barclay) is used specifically for moist-soil. This is the third season for operation of this unit. During year 1, there was a fast drawdown but the pool could not be completely drained. The vegetation and seed production response to the mid-June drawdown was moderate. There also is an indication that salts accumulated,

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particularly in lower sites within the impoundment. After rehabilitation of the unit, complete dewatering was possible. In 1991, the unit was drawdown rapidly on 15 June. Most of the basin has a sparse stand of smartweed (Polygonum persicaria). There also is an indication of spikerushes, chenopods, and what appears to be Atriplex. The most robust growth with the highest density of stems occurs along the high elevations within the impoundment. Some of the smartweeds were blooming and should produce seeds before freeze-up.

Assessment of Barclay--Apparently the fast drawdown in mid-June reduces soil moisture levels too rapidly and there is poor plant establishment. At this late date it is impossible to tell to what extent germination actually took place or if germination occurred but there was high mortality of tiny seedlings. Based on the plant response at the higher elevations in Barclay, the following recommendations seem worthy of testing. The drawdown should be slow to keep soil moisture levels higher for a longer time period. The start of the drawdown should begin at the very beginning of the growing season. The earliest possible drawdown should create the best possible conditions for germination of seeds, and provide conditions for better survival of seedlings. Many smartweeds germinate very early and thus the strategy of an earlier drawdown is suggested to produce a greater density of plants with greater potential for seed production.

As part of the rehabilitation plan, semipermanent units are drawdown. One unit was in the second year of a drawdown. In 1991 the unit was drawn down on 9 June. Vegetation response shows very little millet, but considerable smartweed, chenopods, and Atriplex. sweet clover at the highest elevations suggests that a very early drawdown would result in a extensive and dense stand of clover. Some areas are devoid of vegetation. These occur primarily in ditch bottoms and other depressions at varying elevations within the pool. Possibly salt accumulations are higher at these locations because of evaporation or water left these small depressions so rapidly that poor conditions for germination occurred. There are indications that seed production might range from 200 to over 500 pounds/acre. A question on the best time to flood was discussed; should it be in fall or spring. Shallow fall flooding provides readily available seeds for migrant waterfowl that need to restore lipid reserves lost during migration. Flooding in fall while midges are still active allows the chronomid life cycle to begin in seasonally flooded areas. A group of chironomids have life cycles in which they lay eggs in late summer and fall and the larvae develop over winter and are available as a primary food source for waterbirds in spring. In most environments it is difficult to "conserve" foods and habitats over winter for spring use. There is some potential to provide more foods (seeds) in spring but often impoundments that are not flooded in fall still receive high consumption of foods even if they are not flooded.

A flood irrigated field in Unit 13, with where soils appear richer, has a good stand of millet. Alfalfa was planted on June 15th and there is a nice growth of millet where water flowed through the unit. The stand is especially good at the lower end and in the return flow ditch with good drainage.


5 August 1991

In attendance:

Steve Berlinger, Refuge manager Leigh Fredrickson, Gaylord Laboratory

ALAMOSA NATIONAL WILDLIFE REFUGE

General Overview

Alamosa encompasses 11,000 acres and lies along the Rio Grande River in the eastern portion of the San Luis Valley. The units are old oxbows in which water levels are controlled. The refuge primarily provides breeding habitat for waterbirds. Cattail and bulrush are the dominant robust emergents. Waterfowl production at Alamosa runs about 7,000 birds, the primary species being cinnamon and blue-winged teal, mallard, and pintail. Some sites provide excellent brood water.

Alamosa is operated as a more natural system. Grazing is also used. Some riparian areas and other areas of good forage are overgrazed. Plan to fence the riparian zone with a hot wire to prevent concentration of stock in riparian zones.

Some sites have a cattail problem. The control strategy has been to keep sites dry, but progress has been slow. A drawdown rotation has been initiated in which about half of the units are drained and half have been kept flooded. In units that were dewatered there is evidence of a moist-soil response. The most obvious and consistent response is smartweed. At some sites, cattail is germinating. Thus, there is a delicate balance between response by moist-soil plants and cattail. Other plants germinating in response to the drawdown are spikerush, Atriplex and chenopods. I suspect that if drawdowns were very early that sweet clover would respond as well.

One area has a dense robust stand of Phragmites associated with fresher water along the eastern side and southeastern corner of the refuge. Use some grazing for control but have been thinking about burning this phragmites stand. Stand has been burned in the past.

A canal runs through the refuge and blocks Rio Grande River flood water movement from west to east. The canal is part of a Bureau of Reclamation project that involved the mitigation of 8,000 acres of natural wetland that were lost. Water is pumped into the canal and transported to the Rio Grande River. The system was developed in 5 segments. The last 2 segments use pipes, but the early development was an open ditch system with a plastic liner. The ground water is used to help satisfy the Rio Grande River Compact with Texas and New Mexico. Water Must be of a certain quality (350 ppt TDS or less). Otherwise the water is not considered part of the mitigation. Whitetop is also a problem at Alamosa

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Alamosa gets 4,500 acre-feet of water as part of the mitigation package. Water can be supplied on demand from the canal with electric pumps. Pumps are remotely controlled via a satellite system.

Effective management on the most western sections of the refuge will require construction/rehabilitation of a major water supply ditch.

Moist-soil:

About 250 acres along the BR canal on the north side of Alamosa are dedicated to, or have potential for, moist-soil management. One unit east of the canal has been used for a feasibility study for moistsoil. In 1990 the unit was leveed with a low rice-dike type levee. Soils do not appear nearly as good here as on Monte Vista west of Highway 15. The response to 1990 manipulations was bare soil. The drawdown was around 15 June but was fast because all water was drained in less than 1 day. Russian Knapweed was an aggressive problem. In 1991, about half of the unit . was disked to control knapweed. Knapweed was much reduced from this treatment. Discing was difficult because of the high water table; equipment got stuck and it took a D-7 to get the tractor out.

Area was drawdown rapidly in 1991 and had been irrigated once in 1991. Moist-soil response within the unit has not been good and consists of scattered pigweed, Atriplex and chenopods. However, the pigweed on the levee is excellent. This suggests that an early drawdown and a longer period of soil saturation results in a good growth. The presence and growth of western wheat grass in the unit suggest that salts are not a serious problem.

Recommendations Alamosa moist-soil:

Two approaches seem important. First there might be a poor moistsoil seedbank, but this is unlikely. One strategy that might work is to plant a wild millet. I suggest a millet of a more natural variety and one grown in cooler climates or at higher elevations (sometimes millet seeds sold commercially are imported from other countries and often times from a more tropical climate) be seeded in the fall immediately before flooding. The following spring, the unit should be drawn down around 1-5 June at a very slow rate. Attempts should be made to extend the drawdown over 1 week. Irrigations might improve the growth response and improve survival of seedlings . The first irrigation might be scheduled for 2 weeks after the drawdown. The second at the time of seed head formation. If the drawdown is too early it seems likely that sweetclover may be a problem as is evidenced by the prevalence of sweetclover in adjacent fields. If the site is kept too wet there are many indications that cattail will develop. Preparation for planting millet in fall would have a secondary benefit of controlling undesirable vegetation such as knapweed.


The second approach is to rely totally on the available seedbank but to create conditions that will stimulate the more desirable species. Drawdowns must be slow and most likely should be initiated around June 1. Irrigations of native vegetation also should increase survival and seed production.

General managment overview and recommendations for Alamosa and Monte Vista National Wildlife Refuges

Robust emergents:

Consistent water level management or sites with very high water tables are the most likely to develop monocultures of cattail or other robust emergents. First, the importance of cattail for nesting waterbirds and its importance as a source of detritus for the detrital based food web must be recognized. Thus, a considerable acreage of this important habitat type should be maintained but the sites should have good cover/water interspersion (50:50) over significant portion of each impoundment. Impoundments with problems might be manipulated either by drawdown or a combination of drawdown and vegetation manipulation such as mowing, burning, or disking. Drying sites for at least 2 years may be required to reduce the number of viable rhizomes on sites with a high water table. Mowing and burning, burning and disking, and just burning are additional techniques that should be effective in reducing the number of viable rhizomes. It is likely that slightly different techniques might have to be used on different sites because of differences in soils and hydrology. Some places probably will never dry enough to allow disking but mowing might be possible. Manipulations on some sites might be limited to burning. It will be important to reduce the heavy layer of litter to allow germination of other plants and to release the nutrients tied up in the huge biomass associated with dense stands of cattail. As marshes are regenerated it seems likely that moist-soil type vegetation could be incorporated into the rotation.

Moist-soil management:

There seem to be two ways that moist-soil management can be incorporated into the management of these two refuges. There is evidence that moist-soil techniques can work at . this elevation, in these soils, and under the short growing season. A goal of 100 to 300 acres might be set aside as dedicated moist-soil areas on each refuge. Initially I would recommend an experimental approach to learn about costs, manipulations required, and waterbird use. Thus, this would be a maximum acreage until we are convinced the potential for moist-soil is real and costs are determined for manpower, development, and operation. A second approach is to incorporate moist-soil managment as part of the management regime of semipermanent marshes either as zones of vegetation or as a stage in the regeneration of marshes.

Dedicated moist-soil areas: There is much evidence that moist-soil vegetation is in abundance in the area. However, the response within units designated for moist-soil have been poor, largely because few plants have been established. Indirect evidence suggests that drawdowns must be early and slow. The window for response is very short at this

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elevation thus timing and creating ideal conditions for germination and early growth will be a key to success. If drawdowns occur immediately after ice-out there is evidence that the units might be completely overgrown with clover. As soil and ambient temperatures increase other seed producing annuals are more likely to respond. The apparent problem is that soils likely dry too rapidly for successful germination. Thus initially I would try drawdowns near the first of June. All drawdowns at this elevation should be slow because of the apparent rapid rate of drying: meaning that water should be removed over a period of at least one week. Differences are to be expected in the responses in different units because of soils, salts, history of manipulations, hydrology, water table, etc. Record keeping should be helpful in interpreting the results to improve the potential for management.

Moist-soil in semipermanent marshes: Breeding habitat certainly should be the focus of habitat management on these refuges. Nevertheless there is a unique opportunity to supply resources for migrants and wintering birds in a marsh managment rotation that focuses on providing optimum breeding habitat. Semipermanent marshes should be renovated to improve the distribution and interspersion of vegetation. The most cost effective means is a drawdown. The time of this drawdown, the types of manipulations associated with the drawdown, and the duration of the drawdown all can be directed toward promoting the production of moistsoil resources on a short-term basis (1 or 2 years out of 7 to 15 years). The timing and types of manipulations must be carefully timed to receive these benefits. The overall goal on such sites should be to maintain the high quality breeding habitats but careful planning and implementation of hydrologic and mechanical manipulations should greatly increase benefits provided to a wider group of wildlife.

Marsh Rehabilitation:

It is obvious that marshes on these refuges could benefit from rehabilitation. Scheduling this rehabilitation is a challenge because it is desirable to get as many marshes back into higher production as soon as possible. Nevertheless I would recommend a conservative approach in the number of marshes scheduled for rehabilitation annually for the following reasons: (1) If a large number are rehabilitated in a single year and all come back to a similar condition and then degrade over a similar time, the benefits are less that if a smaller number are rehabilitated each year because some marshes should always be in an ideal situation for waterbird production, (2) environmental conditions within and among years are variable. Thus, ideal conditions for regenerating a marsh do not occur annually and these different conditions result in different plant responses. By scheduling a smaller number of marshes for rehabilitation each year, there is a better change to match the drawdowns with conditions that will produce the best results from the time and effort expended in rehabilitation.

Migrant and Wintering Waterfowl:

Breeding habitat for waterbirds is a critical life requisite and of primary importance at Monte Vista and Alamosa. Currently our poorest understanding of the annual life history of waterfowl is the period from

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brood rearing until arrival on the wintering grounds. During this period young birds must learn how to forage, locate foods, fly long distances to unknown areas, and cope with colder temperatures. Work in Europe with geese suggests that high mortality occurs during this time period and part of the mortality may be related to the amounts, availability, and distribution of foods. The provision of resources during this critical time has been the focus of habitat managers in the South and on migration areas. Unfortunately, little concern for such needs has been apparent on areas generally associated with breeding. Carbohydrates are particularly important during late summer and into early and mid fall for growth of young birds and to restore reserves used during migratory movements. Seeds of annual plants and tubers of perennials are the most common and readily available source of carbohydrates. Management strategies for plants in semipermanent marshes are much different that the strategies required to produce foods high in carbohydrates. Thus, managers of breeding habitats have a great opportunity to supply such resources for migrating waterbirds but they must be well versed in plant ecology and the bioenergetics of waterfowl.

trip report alamosa and monte vista national wildlife refuges

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