Water Quality in Headwater Streams
in the Flathead National Forest

Protecting water quality is a primary objective for natural resource management in the Flathead River Basin according to the Flathead Basin Commission (FBC 1997). Flathead Lake and several large streams in the Flathead Basin have been designated by the Montana Department of Environmental Quality as water quality impaired under the Clean Water Act. One of the key issues in restoring water quality of the impaired waters and protecting water quality elsewhere in the basin is the influence that forest roads and timber harvest may have on water quality.

For well over two decades, managers and scientists have attempted to examine this issue by sampling an array of streams draining small watersheds with varying harvest histories. This effort has been given the moniker, "Headwaters Monitoring Project," to distinguish it from efforts to quantify and control water pollution in the non-forested portions of the Flathead Basin.

In this study we add to the accumulating database concerning forest management effects on water quality in the Flathead Basin. As in previous work, data collection was limited and watersheds were not selected specifically to clearly resolve the issue (i.e., more comparable sites may have existed but the funding was limited and forest managers were reluctant to discontinue the long-term monitoring sites). However, the data were sufficient for some meaningful comparisons of water quality in relation to intensity of forest harvest activity in the few watersheds examined. These watersheds drain the same lithology (Whitefish Range) and are located in the same general area, supporting our rationale for comparing water quality in relation to timber harvest.

In addition to the long-term analyses, annual synoptic surveys of another watershed were conducted in an effort to relate longitudinal changes in the water quality variables to forest harvest and other attributes of the watershed. General Conclusions from this Study:

These results indicated that as the road miles per acre increased in the catchments, total phosphorus and particulate carbon concentrations in the monitored streams increased proportionately. The data also indicated that as the percent harvest increased, nitrate plus nitrite nitrogen concentration in these streams increased proportionately. The statistically significant correlations between higher nutrient concentrations and harvest/road intensity in our time series analyses support the findings of Hauer and Hill (1997). Logging and road building in the Flathead Basin are generally associated with nutrient (nitrogen, phosphorus and more recently, carbon) losses from watersheds. Loading of nutrients to the tributaries of the Flathead River from harvested headwaters are consistently above the background of natural variation when examined with time series monitoring data.

However, no conclusive pattern emerged from the Big Creek synoptics, although nitrate plus nitrite nitrogen and total nitrogen were generally higher in the harvested and roaded areas. Synoptic studies clearly are useful if the objective is simply to obtain a very general understanding of longitudinal conditions in relation to land use within a particular watershed and if the pollution loads are much higher than the background variation (e.g., see Stanford et al. 1997). Much longer-term data are needed to draw definitive conclusions in the highly variable landscapes of the upper reaches of the Flathead River Basin, given the likelihood of significant natural variation in soils, land cover, discharge and other watershed attributes that directly influence nutrient export from watersheds. Assessment of improvements in forest harvest prescriptions or restoration protocols (e.g., road obliteration) cannot be done without long-term monitoring data obtained systematically.

Continued monitoring of the Hand, Tributary of Squaw Meadows and Coal Creek sites is important, if the objective is to quantify changes in water quality as reforestation and other management objectives designed to reduce nutrient loading and water yield are implemented in these particular watersheds. This or a similar "recovery" approach has merit in a long-term monitoring context (and provides background data to assess unplanned events like wildfires). But, continued monitoring of these sites is not warranted in the absence of a more sophisticated and inclusive experimental design (perhaps including these sites) if the objective is to answer the larger question of the basin-wide influences of forest practices on water quality.

It is well known that canopy removal and soil disturbances in forested watersheds usually enhance nitrogen loss rates. Loss rates are higher in nitrogen rich soils. Phosphorus dynamics are more unpredictable because release of occluded P from sediment particles into the dissolved phase depends so much on parent lithology and watershed limnology (i.e., types and distribution of flood plains and other wetlands within the stream continuum). Correlations based on short time-series data as reported herein, simply elaborate that timber cutting and road building, like all other soil disturbances, enhances nutrient runoff and ultimately may contribute to reductions of water quality associated with eutrophication.

What we do not know is precisely how much nutrient loading is associated with the legacy of timber management in the Flathead Basin and the extent, if any, that modern management prescriptions may be reducing the loads. This information is absolutely essential in improving water quality under the statutes of the Federal Clean Water Act and responding to broad public support for maintenance of high water quality in the Flathead Basin. We know that harvest/roading is having an effect, we just do not know by how much. We also do not know to what extent this pollution may be attenuated by recycling and storage processes associated with transmission of the load through the large flood plain wetlands that predominate throughout the mountain and piedmont valley segments of the river system. Accurate estimates of the contribution of land use associated with timber management to the eutrophication problems in Flathead, Swan and Whitefish and other economically important lakes that are on the receiving end of runoff in the Basin cannot be made in the absence of this information. Long-term monitoring of sites that have not had timber management activities or roading in the catchment also is needed to assess the natural range of variability in nutrient and sediment transport given 'natural' disturbances such as flood or fire.

We stress that controlled experimental designs, including, for example, pairs of headwater sub-basins of similar biophysiography, with and without harvest and roading of similar prescription, and long-term data (> 5 years) are required to clearly and unambiguously quantify the effects of forest management on water quality in the Flathead Basin. We strongly recommend much greater investment in a more sophisticated, basin-wide and long-term approach.