C2 Implications of Rivers and Reservoirs
Fast-moving offensive ground forces that lack sufficient air assault capabilities must swim, ford, ferry
across, or build bridges over large streams without breaking stride or forfeit forward momentum while defenders on
the far bank hold in place. All military services routinely require adequate water for drinking, cooking, and
sanitation, plus special purposes such as decontamination during chemical combat, Drainage systems, river crossing
sites, and militarily useful reservoirs thus are relevant topics.
Drainage systems. Drainage systems generally are shaped like asymmetrical trees, each branch of which
empties its contents into a larger stream until the biggest tributaries connect with the trunk. Immense systems such
as the Amazon and Mississippi funnel runoff from several million square miles, while minor systems service much
smaller areas. Great rivers that arise and remain in well-watered regions have many smaller areas. Streams 30 to 60
feet wide (9 to 18 meters), for example, lace Western Europe every 6 miles (9+ kilometers) or so, while rivers up to
300 feet across occur on average at 30-mile intervals. Relatively few branches in contrast feed the Tigris, Euphrates,
and Nile, which arise where water is plentiful but traverse dry lands thereafter.
Militarily important riverine characteristics begin with widths, measured in feet, yards, or meters from bank
to bank, and with depths which indicate the distance from surface to bottom (figure 5). Current velocities, usually
stated in feet or meters per second, depend primarily on the steepness of the stream bed. Twenty-five to 30 feet (7-9
meters) per second or 17 to 20 miles an hour is considered quite fast, whereas 1 or 2 feet per second or less is
sluggish. The deepest, fastest flow normally follows the main channel well above the bottom, because stream banks
and beds function as friction brakes. Currents accelerate along outside curves, where they figuratively play crack the
whip.
Widths, depths, velocities, and volumes measured in cubic feet, yards, or meters past particular points are
by no means constant. Military planners and operators anticipate seasonal fluctuations, typified by annual
inundations along the Nile Valley, and are fully aware that tidal rivers rise and fall twice daily in response to lunar
cycles. Not all destructive floods, however, are predictable nor are they from natural causes: German defenders in
November 1944 blew dams on the Roer River at Schmidt to delay advancing Allied armies; Chinese “volunteers” at
Hwachon Reservoir in Korea (1951) threatened to release a wall of water that could have washed away command
posts, supply dumps, and bridges and split U.S. IX Corps.
Sand bars, mud banks, and rock outcrops impose natural obstacles close to shore, especially along outside
curves. Floating debris and ice floes in stream can be destructive to river craft and bridges, but solid ice is beneficial
when thick enough to bear the weight of troops, trucks, and tanks.
Crossing sites. River crossings at many places on broad fronts minimize enemy abilities to concentrate
decisive defensive power against vulnerable targets, perhaps employing weapons of mass destruction. Ideal
locations exhibit the following attributes:
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Good roads closely parallel the river so that offensive forces can easily reach the best crossing sites
Well protected areas are ample to hold follow-on forces waiting to reinforce assault waves
Easily negotiable slopes lead to water on the near shore and to land on the far side
Narrows facilitate fast assault crossings, round trips by raft and ferries that support subsequent buildups,
and combat bridge construction.
Current velocities less than 5 feet per second (3.5 miles per hour) limit down-stream drift
Fording sites are consistently shallow, their bottoms are firm enough to bear heavy traffic, and selected
routes are free from militarily significant obstacles
Unfordable streams are consistently deep enough to float swimming vehicles, inflatable boats, rafts, and
ferries
Rapids, shoals, sandbars, snags, debris, and icy obstructions are conspicuously absent
Conveniently located islands that act as stepping stones reduce combat bridging requirements
The best crossing sites unfortunately are apt to be staunchly defended and actual conditions seldom are ideal.
German panzer divisions in Russia during World War II, for example, frequently found that marshy lowlands
abutted both banks of large streams, floods loaded with sediment clogged inboard engines, ice floes each spring
bombarded expedient bridges, and vehicles became toboggans on moderate slopes after torrential summer rains.
Skilled tacticians nevertheless overcame such adversities and learned that landings at unexpected spots improve
prospects for low-cost success.
Water Supplies. Large armed forces demand enormous quantities of water in peacetime as well as war,
whether active or passive, at fixed installations or in the field. Requirements are most difficult to satisfy in arid
regions, especially when division-sized ground elements and air wings move frequently. Drinking water must be
palatable (color, odor, and taste all count) and be unpolluted by pathogenic bacteria that spread contagious diseases
such as typhoid fever, cholera, and amoebic dysentery. Time-consuming and expensive purification processes
become obligatory when water for use as coolants is corrosive. Surface and subsurface sources are complimentary,
because neither suffices under all conditions. Both contribute supplies that differ quantitatively as well as
qualitatively from time-to-time and place-to-place with varying degrees of convenience.
Surface water. Rivers, lakes, and some inland seas are large sources of fresh water on Earth’s surface.
Lesser repositories include ponds, small streams, and springs. Some sources are consistently reliable, whereas floods
and droughts elsewhere seasonably reduce useable water supplies below required amounts. Unpredictable depletions
caused by nature or enemy actions may do likewise with little or no notice. Unpredictable depletions caused by
nature or enemy actions may do likewise with little or no notice. Prudent commanders consequently try to identify
alternative sources before water crises occur.
Perennial flows of sweet, cool spring water usually are low in organic impurities but tend to be widely
scattered, high in mineral content, and output seldom is enough to satisfy large military formations which most often
must establish, operate and maintain water supply points at locations that are easily accessible and facilitate
distribution by road. Large quantities of good quality surface water are commonly available on plains and plateaus
where rainfall annually exceeds 25 inches (60 centimeters), but ample sources are hard to find in mountains where
runoff starts, in frigid climes where sources are ice-bound many months each year, in the tropics where pollution
frequently is rampant, and near small towns and urban centers where raw or incompletely treated sewage and toxic
chemicals sometimes contaminate running water and reservoirs.
Naval vessels and some coastal countries distill brine to produce fresh water. The world’s largest
desalinization plant, located in Saudi Arabia, siphons more than 5 million gallons per day from the Persian Gulf
(nearly 19 million liters) and, after purification, pipes fresh water as far inland as Riyadh. Allied missile defense
batteries took special precautions to protect that facility against Iraqi Scud attacks during Operations Desert Shield
and Desert Storm in 1991-1994. The U.S. Marine garrison at Guantanamo Bay, Cuba, which is isolated from the rest
of Oriente Province by minefields and other man-made obstacles, routinely requires about 1.2 million gallons (4.5
million liters) of desalinated sea water per month. Surplus capacity and barges, plus 15 million gallons in storage,
made it possible to accommodate 55000 Cuban and Haitian refugees who inflated peak consumption to more than
73 million gallons in October 1995 (27.6 million liters).
Subsurface Water. Not all precipitation and melt water empties directly into surface drainage systems. A
good deal seeps into subterranean reservoirs instead. How much depends on total accumulations, slopes, soil
compositions, and the permeability of underlying rocks. Moisture first percolates through an aerated zone that
alternately dampens and dries, then reaches the water table, a saturated layer of variable thickness and depths that
may be shallow or deep (figure 6). Some water continues to trickle down through cracks and crannies until
contained by aquifers encased in nearly impervious rock formations. Artesian springs that rise to the surface under
hydrostatic pressures along fissures and fault lines are little affected by seasonal fluctuations or by pollution, but
often are too mineralized for human consumption or cooling systems. Relatively slow wells sunk into the water table
generally are preferable with two prominent exceptions: well water along littorals tends to be brackish; supplies
drawn from arctic sources above permafrost are only briefly productive each year.
Mobile ground forces seldom sit still long enough to tap subsurface reservoirs, but ports, airfields, supply
depts., major maintenance teams whose humanitarian mission is to improve the quality of life for impoverished
people. Subterranean repositories furnish the only reliable source of water inland wherever lands are parched, a fact
of particular importance when summer heat heightens routine requirements and demands soar under stressful
conditions. Conservative estimates, for example, indicate that it would take approximately 200,000 gallons of wash
water to decontaminate the personnel, weapons, equipment, and facilities (such as aid stations and field hospitals) of
just one U.S. Army or Marine division hard hit by persistent chemical warfare (CW) agents. That would be a tall
order even if fire hydrants were handy, and perhaps impossible in the dessert, where the employment of CW
munitions could entail unconscionable risks for both sides if reprisals in kind drenched aggressors.
Source: Collins, J. M. (1998). Military geography for professionals and the public. Washington DC: National
Defense University.