James Maxwell in the Spring issue of the Watershed Management Council Newsletter suggested some concepts that might benefit from further discussion.

He suggested that after some "prudent" management activity ( perhaps roading and timber harvesting in some prescribed way), time itself would be sufficient to restore the forest's protective and productive functions to something "in the range" of the original level; that is, "reset" the forest condition so that it functions essentially as it did before the activity, and further, that this condition is an "equilibrium" condition that maintains itself over time. Imbedded in this concept is the expectation that prudent management allows for the effect of the full range of expected (or possible) meteorological event to occur on the watershed during the "reset" period. In making such allowance we must be sure that:

1. At no time during the reset period, do any combination of conditions created by management followed by possible meteorological events cause permanent damage to the watershed, such as:
a. Change in the absorptive capacity of the surface;
b. Loss of the detention and retention capacity of the vegetation
and soil, such as soil loss from the soil surface or channels;
c. Creation of revegetation problem areas;
d. Loss of channel capacity to carry flood waters.

2. At no time during the "reset" period does a condition occur that destroys a resource, such as:

a. water quality
b. fish stocks
c. site quality/productivity
d. scenic values;
f. stability against landslide damages

Let's examine the concept of "prudent management". We might reason that some small damage might be acceptable. However, if we consider the cumulative consequences it may turn out that "worst case avoidance" is the only acceptable criteria. If any combination of management-imposed changes in watershed conditions and possible meteorological events can destroy a watershed function, even though the probability is low, eventually the damage will occur to all such managed watersheds. We need only to look at areas of the Mediterranean and Middle East for examples of the effects of persistent misuse.

The concept of watershed conditions "resetting" themselves and of some "equilibrium" conditions being attained seem to be useful chiefly as goals rather than expectations. More useful concepts might be the rate of creation or recovery of watershed attributes and their duration.

To make management decisions based on acceptable or compensatable hydrologic effects, for example, we need to know how the activity (as actually performed) changed flooding, sedimentation or water supply attributes /1/.

Whether we term our desideratum "reset" or "recovery," it is important to define recovery of what attributes and from what impacts. What attributes of watershed or sites within watersheds that we wish to at least maintain are well known (although sometimes not well quantifiable).

From what we wish to defend these watershed or site attributes involves interactions between events and watershed and site conditions. These involve difficulties in quantifying, for the crucial events may be rare and poorly measured. The watershed or its characterization requires that they be expressed in terms that are meaningful only when some threshold of a combined conditions and event is exceeded. A single event may change the threshold for a succeeding event. For example, the 1964 flood event in northern California delayed the recovery from the 1955 flood, which was in turn delayed by conditions of poor logging practices /2/.

Looking further, we ask why is the "resetting" or "recovery" of a watershed hydrologic condition a sufficient goal? That condition was the result of unprescribed mis-management starting with uncontrolled forest fires from lightning, burning by early Indians, disturbance by mining, overgrazing and burning by sheepmen, and progressing most recently to roading, timber harvesting and type conversion. Perhaps we should ask if we can find ways to enhance rather than merely reset present watershed performance.

/1/ Estimating hydrologic values for planning wildland fire protection. 1982 by Henry Anderson and Clinton A. Philips. USDA General Technical Report, PSW-58, IN: Symposium on the dynamics and management of Mediterranean type ecosystems. San Diego State University. June 23-26, 1981 pp 411-416.

/2/ Major floods, poor land use delay the return of sedimentation to normal rates. 1972 by Henry Anderson. USDA-Forest Service Res. Note, PSW 268, 4 pages.

Principal component analysis of watershed variables affecting suspended sediment discharge after a major flood. 1970 by Henry Anderson. Intl. Assoc. Sci. Hydrol. Publ. 90 pp 409-416.