Science of Water : Concepts and Applications

Introduction 3
On second look, we see that the fundamental characterization of this particular pool’s surface is
correct enough. Wedged in a lonely riparian corridor—formed by river bank on one side and sand
bar on the other—between a youthful, vigorous river system on its lower end and a glacier- and
artesian-fed lake on its headwater end, almost entirely overhung by mossy old Sitka spruce, the
surface of the large pool, at least at this particular location, is indeed still. In the proverbial sense,
the pool’s surface is as still and as fl at as a fl awless sheet of glass.
The glass image is a good one, because, like perfect glass, the pool’s surface is clear, crystalline,
unclouded, defi nitely transparent, yet perceptively deceptive as well. The water’s clarity, accentuated
by its bone-chilling coldness, is apparent at close range. Further back, we see only the world
refl ected in the water—the depths are hidden and unknown. Quiet and refl ective, the polished surface
of the water perfectly refl ects in mirror-image reversal the spring greens of the forest at the
pond’s edge, without the slightest ripple. Up close, looking straight into the bowels of the pool we
are struck by the water’s transparency. In the motionless depths, we do not see a deep, slow-moving
reach with muddy bottom typical of a river or stream pool; instead, we clearly see the warm variegated
tapestry of blues, greens, and blacks stitched together with threads of fi ne, warm-colored sand
that carpets the bottom, at least 12 ft below. Still waters can run deep.
No sounds emanate from the pool. The motionless, silent water does not, as we might expect,
lap against its bank or bubble or gurgle over the gravel at its edge. Here, the river pool, held in temporary
bondage, is patient, quiet, waiting, withholding all signs of life from its surface visitor.
Then the reality check: the present stillness, like all feelings of calm and serenity, could be
fl eeting, momentary, temporary, you think. And you would be correct, of course, because there is
nothing still about a healthy river pool.
At this exact moment, true clarity is present, it just needs to be perceived … and it will be.
We toss a small stone into the river pool, and watch the concentric circles ripple outward as the
stone drops through the clear depths to the pool bottom. For a brief instant, we are struck by the
obvious: the stone sinks to the bottom, following the laws of gravity, just as the river fl ows according
to those same inexorable laws—downhill in its search for the sea. As we watch, the ripples die away
leaving as little mark as the usual human lifespan creates in the waters of the world, then disappears
as if it had never been. Now the river water is as before, still. At the pool’s edge, we look down
through the massy depth to the very bottom—the substrate.
We determine that the pool bottom is not fl at or smooth, but instead is pitted and mounded occasionally
with discontinuities. Gravel mounds alongside small corresponding indentations—small,
shallow pits—make it apparent to us that gravel was removed from the indentations and piled into
slightly higher mounds. From our topside position, as we look down through the cool, quiescent
liquid, the exact height of the mounds and the depth of the indentations is diffi cult for us to judge;
our vision is distorted through several feet of water.
However, we can detect near the low gravel mounds (where female salmon buried their eggs,
and where their young grow until they are old enough to fend for themselves), and actually through
the gravel mounds, movement—water fl ow—an upwelling of groundwater. This water movement
explains our ability to see the variegated color of pebbles. The mud and silt that would normally
cover these pebbles have been washed away by the water’s subtle, inescapable movement. Obviously,
in the depths, our still water is not as still as it fi rst appeared.
The slow, steady, inexorable fl ow of water in and out of the pool, along with the up-fl owing of
groundwater through the pool’s substrate and through the salmon redds (nests) is only a small part
of the activities occurring within the pool, including the air above it, the vegetation surrounding it,
and the damp bank and sandbar forming its sides.
Let’s get back to the pool itself. If we could look at a cross-sectional slice of the pool, at the
water column, the surface of the pool may carry those animals that can literally walk on water. The
body of the pool may carry rotifers and protozoa and bacteria—tiny microscopic animals—as well
as many fi sh. Fish will also inhabit hidden areas beneath large rocks and ledges, to escape predators.
Going down further in the water column, we come to the pool bed. This is called the benthic