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Papers by Raymond V. Corning

I felt a recently completed paper of mine might be of interest to various members and to newspaper writers in the West. It is entitled: "Diminished Sweetwater River Flows From the High Cold Desert Region." (Wyoming).

Habitat conditions of the Bureau of Land Management's Green Mountain Common Allotment, a site of much controversy over the past year, and probably this year, is covered in depth in the paper. Habitat conditions of the Granite Creek Common Allotment are also covered in depth. The two allotments vary in reasons for their existing problems, but not in the results of the problems.

Water storage within the riparian wetlands has been badly diminished in both allotments with a resulting decrease in continuous stream flows.The damages are due almost solely to cattle grazing in the case of the Green Mountain Common Allotment. Riparian wetland problems occurring in the Granite Mountain Open Allotment were caused by a combination of cattle and wild horse grazing.

Riparian wetlands of Green Mountain and Granite Mountain Common Allotments have historically furnished much of the downstream water supply, as they have in other allotments within the Sweetwater River Drainage. These riparian wetlands may have formed as early as 2,000 years ago. Sheep were grazed for many years in much of this area with little lasting damage to riparian wetland areas. All this changed when sheep were replaced with cattle in the 60s and early 70s. Cattle grazing has nearly eliminated the water retaining capabilities of the various riparian wetlands in less than 50 years. Centuries of humic accumulation no longer exist. The means by which this has occurred is documented, as is the actual damage. I believe the 12 photos of riparian wetlands tell a poignant story of the plight of these riparian wetlands.

Unlike many BLM administered lands, the High Desert Cold Region receives most of its precipitation in the form snow. Retention of the snow in desired areas is a major problem as nearly constant winds prevail in the region. Preliminary calculations indicate that riparian areas, and riparian wetlands, retain around 72 times more snow if vegetative cover attains a height of 14 inches by snowfall, instead of the more common two inches that frequently remains at the end of each grazing season. Other damages that adversely impact riparian wetlands as a result of use by cattle are also documented.

While many public lands of the West do not have riparian wetlands more dependent on snow then rainfall, most cattle impacts occurring in the Sweetwater River Drainage are common in other regions. Hoof damage, and other cattle related problems, are the same no matter if snow or rain provides the major source of water supply.

The local drought that may be entering the third year has only emphasized the importance of good functioning wetlands. Plans are already being made for hauling water for cattle in several places within the Green Mountain Common Allotment. The Casper Star recently ran an article indicating that irrigation water of the North Platte River drainage (which encompasses the Sweetwater River Drainage) may be severely restricted this summer above Pathfinder Reservoir. Any irrigators holding water rights that were established after 1904 may receive no water at all. Other areas of the drainage may also face severe water shortages. Well functioning riparian wetlands could have made a significant difference during this period of drought, both locally and within the State.

Diminished Sweetwater River Flows From the High Cold Desert Region is available in both HTML format, and as an 11mb PDF format file. A free Adobe Reader can be obtained at: if you do not already have it on your computer. Or, if you wish to review or print the paper at your leisure, the PDF file can be saved to your hard drive and read with the Adobe Reader.

The paper below was written in the hopes of convincing the Environmental Protection Agency to address water fluctuation as a stressor of streams because it is as important as many pollutants, and pollution now addressed. My plea fell on deaf ears.

The linked Stream Stressors - Water Fluctuation, Sedimentation, and Erosion


By: Raymond V. Corning
Lander, WY 82520

The most visually noted forms of stream stress in or along streams within overgrazed rangelands are usually sediment deposits and erosional alterations of instream and stream bank habitat. The stressors sedimentation and erosion are also most evident in streams recently impacted by extensive road construction, recent urban development, or recently deforested areas. However, the one stressor that causes the most adverse impacts as a result of overgrazing, urban development, and extensive road construction, is seldom visually apparent. It is water fluctuation that causes the most damage to stream life, wetlands, and riparian vegetation (which can only be viewed over time), not stresses induced by sedimentation and erosion. Not only does water fluctuation stress stream systems in many ways, but water fluctuations are the mechanism through which sedimenting and eroding environs occur.

Stresses from water fluctuation are particularly strong if both upland and riparian habitats have been denuded. Wherever strong erosional or sedimenting conditions are noted, no matter what initiated them, an in depth investigation will reveal water fluctuation is strongly influencing stream biota. Unfortunately, many investigators blame sediment and erosion for major declines in stream productivity, without looking beyond the obvious. When evaluative techniques are applied to sedimentation and erosion, the measured impacts seldom are great enough to explain why earlier existing aquatic populations declined to the degree noted. Very few field studies have been adequately designed to separate the effects of water fluctuation from those of sedimentation and erosion. Therefore, there is a strong need to study the three as a unit.

A lack of vegetation on uplands as a result of over grazing, or clear cutting of timber, speeds the movement of water over the uplands, leading to surface, or rill erosion. This, in turn, speeds the movement of sediment laden water to stream systems. Sparse upland vegetation also speeds the movement of water into streams along with inducing surface erosion. If riparian and wetland vegetation is missing from stream edges, or has been heavily cropped as a result of grazing, the time it takes storm runoff to reach the stream is further reduced (as vegetation acts as a major buffer to water runoff). In cases of road construction, airport construction, or urbanization, replacement of vegetation with impervious materials shortens the time it takes water to reach a stream even more than for over grazed or recently clear cut timber areas, because the use of impervious materials generally requires installation of storm drains. In turn, these drains generally empty directly into nearby streams. Anderson (1970) found that the streams utilized in his studies of northern Virginia streams, flood ".. lag time for a completely storm-sewered system is about one-eighth that of a comparable natural system, while storm sewering of only the tributaries (main channels unlined) reduces the lag time to about one-fifth that of a comparable natural system." Population of the region was around 400,000 at the time of Anderson's study, and now is around one million or more. Runoff lag times have probably increased even more, in direct relationship to the overall population increase..

Under ideal conditions, where upland and lowland vegetation is lush, and riparian and wetland habitats are in excellent shape, water from a storm event may remain in a watershed as ground water for weeks or even months before exiting the mouth of a stream as stream flow. Where impervious materials exist in significant quantities, or the land has been partially or completely denuded through over grazing or timber clear cutting, the retention of storm water within a watershed is more frequently measured in hours or days. Thus, ground recharge of the underground water table is thwarted by overgrazing; the widespread placement of cement and asphalt cover within urbanized areas; the development of impervious cover due to roadway construction; or, by both urban and roadway designs which encourage rapid transport of water directly into stream systems.

Area geology affects the severity of impacts, for the stressor water fluctuation is more pronounced and more damaging to streams entrenched in sedimentary strata. Streams underlain by metamorphic or igneous formations restrict ground water recharge naturally, so runoff is normally rapid from these areas. The resistive nature of streams overlying metamorphic or igneous formations also better adapts them for receiving abnormal stream discharges, but at the expense of existing aquatic populations.

Streams surrounded by uplands that have been heavily overgrazed follow a pattern of rapid stream discharges after storm events, rapid rises in flow rates, and swift returns to pre-storm event stream levels. During drought and hot summer periods, because of reduced ground water recharge, stream flow is characteristically reduced below "pre-overgrazing" times. In the most advanced stages, streams that were formerly free-flowing year around may become intermittent or even ephemeral streams. Tincup Creek, a third order stream near Jeffrey City, Wyoming, is a typical example. In 1955, the stream maintained a perennial flow, but now (1998), it is an intermittent stream (Corning, 1989). Changes in thermal conditions generally occur along with the changes noted above, which lead to increased exposure of water in a stream to the heat of the sun, e.g. slower water movement, stream widening, and reduced stream cover to shade the stream from thermal rays. The same stressors occur in streams impacted by urban development, road construction, or recent deforestation.

Stresses induced by erosional widening or deepening of a stream, and sediment deposition, are also brought into play on streams affected by strong stream flow fluctuations. Widening of a stream that is already experiencing decreased groundwater recharge not only reduces flow rates by spreading water over a wider stream area, it also has adverse impacts on aquatic habitat. Also, in heavily sedimented reaches of a stream, stream flow may be confined to areas below the surface of the sediment. A catastrophic event released large quantities of sand and gravel into Lone Pine Creek, Colorado, and most of the flow was confined to underground flow during the summer. The trout population was virtually eliminated by fall because fish were confined to pools and were easy prey for raccoons (Corning, 1969). And, when streams deepen, riparian vegetation dependent on occasional flooding, may give way to less stable dry land vegetation.

Specifically, what are other stresses related to water fluctuations? Rapid runoff of storm event water means flows frequently exceed the speeds at which stream biota can remain in their normal habitat, e.g. fish may be swept downstream. B. Harvey (1987) studied Briar Creek, Oklahoma, during a June, 1985, flood and found that centrarchids and cyprinids smaller than 10 mm total length were extremely susceptible to downstream displacement. Fish eggs, and young of other organisms which normally inhabit stream gravel, may be disinterred and thus perish. Hanson and Waters (1974) stated floods in late winter and early spring of 1965-1966 severely affected brook trout eggs and fry of Valley Creek, Minnesota. The 1965 and 1966 classes of brook trout were nearly eliminated. Corning (1969) placed fertilized rainbow trout eggs in baskets and artificial redds in Sheep Creek, Colorado. Altogether, 75% of the eggs were washed away by high flows shortly after emplacement. Seegrist and Gard (1972), in a study conducted on Sagehen Creek, California, found that following winter floods brook trout (fall spawners) recruitment was small, with rainbow trout (spring spawners) recruitment much higher. The reverse situation was found to exist when major floods occurred in the spring rather then the winter.

High flows, which markedly increase sediment movement, may scour periphyton and other sessile forms of organisms from their normal habitat. Scraper insect larvae, if not swept away, may still decline because of a decreased food supply. Glova, G. J. and M. J. Duncan (1985), while studying a large braided river in New Zealand, came to the conclusion "[t]he major impact of floods on rearing environments seems to be that of their destructive effects on the food supply for fish." High flows also increase erosional stress by increasing the cutting forces of transported sediments, and streams either widen further or they down cut. If down cutting occurs, water tables for riparian and wetland vegetation are lowered, and if this continues riparian and wetland species are eventually replaced by dry land species as periodic water replenishment is no longer possible. Numerous U.S. Bureau of Land Management streams in the West have down cut, because of overgrazing of riparian habitat and the resulting loss of willow cover. Many of these streams have been unable to re-establish willow cover, even through artificial plantings, because water tables are below those necessary to maintain any but dry land vegetation.

Flooding also erodes stream banks that are no longer protected by riparian or wetland vegetation. On the other hand, sediment builds up in slower moving parts of the stream, frequently filling interstitial niches in cobble and large gravel. As flows recede further, sediment may even coat areas that were formerly completely free of sediment. During a study of Valley Creek, Minnesota, Hanson and Waters (1974) found no initial mortality among yearling and older brook trout. However, the fish suffered delayed mortality, which was attributed to reduced habitat. Again, strong stressors are placed on both sessile and free moving organisms.

Additional stresses are placed on stream organisms when day to day stream flow decreases. Decreases in ground water recharge into streams generally increases day time water temperatures by reducing the mix of cooler recharge waters with surface waters. The loss of ground waters also increase stream temperatures by reducing the quantity of stream water available to absorb heat produced by sunlight. When stream flow decreases, pools are reduced in depth, and riffles may be eliminated. Decreased flow means the wetted perimeter of the stream is reduced, or if erosion has widened the stream, the wetted perimeter may be increased, but stream depth may be significantly reduced, flows may slowed, and water temperatures may increase beyond acceptable levels for some stream biota. Logging can be particularly devastating, "[b]oth the mean [water] temperature and diel fluctuation within the gravel increased in relation to the extent of logging." The cutthroat trout population of the affected stream was still about one-third that of the pre-logging population, six years after logging ceased. "The sizeable temperature gradients we encountered were probably caused partly by reduced interchange of surface and intragravel water as a result of sedimentation." (Ringler, N. H. and J. D. Hall, 1975). Although benthos production was not directly related to stream flow fluctuations in Sheep and Lone Pine creeks, Colorado, overall production of benthos varied directly with the wetted perimeter. (Corning, 1969).

It is my recommendation, based on the foregoing discussion, that since strong inter-relationships exist between Flow Alterations, i.e. Instream Flow Water Fluctuation, Sedimentation and Erosion, all three should be combined for review, study, and future recommendations, rather than being considered at different time periods. Habitat Alteration, other than Flow Alterations, should also be included since it is habitat alteration that ultimately increases water fluctuation. Sedimentation and Flow Alterations appear in at least three sections of 40 CFR Part 131 Water Quality Standards Regulations; Proposed Rule.

Without habitat alteration, there would be no unnatural flow alterations, without flow alterations there would be no unnatural sedimentation and erosion. Good TMDL development will require good stream flow data in order to determine high, low, and average stream flows, as will the solving of instream flow water fluctuation. If the proper best habitat management measures are employed (substitute urban runoff measures for urban areas), the highs, lows, and extreme lows of altered flow can be controlled. The combination of proper habitat best management measures, and "within balance" instream flows, should lead to "within balance" sedimentation and erosion. However, habitat alteration stressors other than Flow Alterations need to be determined and narrative criteria developed for these stressors.

Water flow data sufficient to determine high flows, average stream flow, and low flows, has already been mentioned as a need, and therefore should be incorporated as means for establishing stressor criteria. The stressor suspended sediment is probably best measured via a depth-integrating suspended sediment sampler operated within the thalweg. Particles should be weighed, not determined through light extinction methods (Duchrow, R. M. and W. H. Everhart, 1971). All light extinction methods are susceptible to the colors of the various particles in suspension, and therefore give variable results with changes in particle colors.

Bed-load movement, a potential stressor, is particularly hard to determine, but rough formulas exist for estimating bed-load movement. (Chow, 1964). During the 20th century bed-load movement has been ignored, hopefully it will not be ignored during the beginning of the 21st century. The U.S. Geological Survey and other appropriate offices should be consulted concerning the best methods currently available (with time of sampling and estimation both factors in determining "best").

Good equations and methods for determining the potential stressors of urban runoff, timber clear cutting, and timber "thinning" also need to be searched out, and should be used to develop suitable criteria for these stressors.

From the foregoing, it should be patently obvious that "one shot" sampling for TMDLS (particularly during low flows) will not answer the hard questions that need to be answered. The need for narrative standards, rather than numerical, should also be obvious.

Causes and Effects of Decreased Vegetative Cover



ANDERSON, D. G. 1970. Effects of urban development on floods in northern Virginia. Geol. Surv. Wat.-Sup. Pap. 2001-C; U.S. Gov. Pr. Office.

CHOW, V. T. 1964. Handbook of Applied Hydrology. 1-1 - 29-30. McGraw-Hill Book Co.; New York.

CORNING, R. V. 1998. Personal communication, Jack Scarlet, Lander, WY.

CORNING, R. V. 1969. Water fluctuation, a detrimental influence on trout streams. Proc. 23rd Annual Conf. Of the Southeastern Assoc. of Game and Fish Comm: 431-454.

CUNJAK, R. A. and J. M. GREEN. 1984. Species dominance by brook trout and rainbow trout in a simulated stream environment. Trans. Amer. Fish. Soc. 113(6):734-743.

DUCHROW, R. M. and W. H. EVERHART. 1971. Turbidity measurement. Trans. Amer. Fish. Soc. 100(4):682-690.

GLOVA, G. J. and M. J. DUNCAN 1985. Potential effects of reduced flows on fish habitats in a large braided river, New Zealand. Trans. Amer. Fish. Soc. 114(2):165-181.

HANSON, D. L. and T. F. WATERS. 1974. Recovery of standing crop and production rate of a brook trout population in a flood-damaged stream. Trans. Amer. Fish. Soc. 103(3):431-439.

HARVEY, B. C. 1987. Susceptibility of young-of-the-year fishes to downstream displacement by flooding. Trans. Amer. Fish. Soc. 116(6):851-855.

RINGLER, N. H. and J. H. HALL. 1975. Effects of logging on water temperature and dissolved oxygen in spawning beds. Trans. Amer. Fish. Soc. 104(1):111-121.

SEEGRIST, D.W. and R. GARD. 1972. Effects of floods on trout in Sagehen Creek, California. Trans. Amer. Fish. Soc. 101(3):478-482.