Title: Letter 7/26/1976
Full Citation
Permanent Link: http://ufdc.ufl.edu/WL00002257/00001
 Material Information
Title: Letter 7/26/1976
Physical Description: Book
Language: English
Spatial Coverage: North America -- United States of America -- Florida
Abstract: Letter 7/26/1976, To: LM Blain, From: Robert Atchison, Enclosed 'Water Crop' Draft
General Note: Box 10, Folder 12 ( SF Water Rights-Water Crop - 1973, 1976-77 ), Item 21
Funding: Digitized by the Legal Technology Institute in the Levin College of Law at the University of Florida.
 Record Information
Bibliographic ID: WL00002257
Volume ID: VID00001
Source Institution: Levin College of Law, University of Florida
Holding Location: Levin College of Law, University of Florida
Rights Management: All rights reserved by the source institution and holding location.

Full Text

southwest Flncida
Water Manageement District

P. 0. BOX 457

DERRILL McATEER, Chairman, Brooksville
J. R. GRAW, Vice Chairman, Ocala
JOE E. HILL, Treasurer, Leesburg

July 26, 1976


THOMAS VAN DER VEER, Secretary, Yankeetown RONALD B. LAMBERT, Wauchula
N. BROOKS JOHNS, Lakeland LEWIS H. HOMER, Clearwater
C ? D Id R. Feaster, Executive Director
RJUL 2 1976

JUL 2 7 1976

By ------.... __ _--

Mr. L. M. Blain, Esquire
P. 0. Box 1363 "
Tampa, Florida 33601
Dear Buddy:

The enclosed Water Crop slide presentation script
comments made by yourself and the staff. I would
your reviewing it by August 10th and returning to


Public Information Officer



cc: E. D. Vergara





The first recorded instance of anyone having reasoned
that rainfall feeds lakes, rivers and springs occurred in
the late 1600's. Halley, the famous English astronomer,

totalled up the amount of water flowing in rivers that
lead to the Mediterranean Sea and discovered that their
combined flow ft roughly equal to the water in the rain
and snow that b)ih4 on the area drained by the rivers.
Almost simultaneously two Frenchmen, Perrault and Marriotte,
made very nearly the same discovery. They measured the

flow of rivers in their area and found that flow to be
about equal to the amount of rain and snow there.

In the late 17th century this correlation was almost earth-
shaking in nature. Now, nearly 300 years later, it's

almost common knowledge.

Water is constantly being exchanged between the earth and

the atmosphere. The "power source" for the exchange is the
heat of the sun and the pull of gravity. Water evaporates
from the ground, from vegetation, isw lakes, ponds, streams,

rivers and oceans. It is carried in the air as water vapor.
Eventually, the vapor cools and condenses, changing from
vapor to a liquid -- and then it falls again as rain.

The rain feeds the lakes and rivers. From there, the water
is carried to the ocean. From the ocean -- and other open-
surfaces -- it w|n and returns to the atmosphere,

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once again to turn to rain in a continuous, unbroken cycle.

Water goes from earth to air, from atmosphere to earth

again and again. Consequently, the exchange is called

the hydrologic cycle -- hydro meaning "having to do with

water" and loge, the Greek work meaning "knowledge of."

The hydrologic cycle functions within the hydrologic system.

This system conveys all water from where it falls as rain

to the Gulf or to the atmosphere. All streams, lakes,

springs, sinks and aquifers are part of this water-conveying


Water enters the hydrologic system as rainfall and is

temporarily stored in streams, lakes or aquifers while

enroute to the area's discharge points. When the rainfall

has been heavy, the rate of recharge to the aquifers for

the area usually exceeds the rate of discharge from the

area. This means that more water will be stored in the

area -- usually within the aquifer--than will be released

from it. Consequently ground water levels will rise.

When the discharge rate exceeds the recharge rate -- the

volume of water in storage declines and ground water levels


The characteristics of the hydrologic system vary regionally

within the District, although its water-conveyance principal

remains the same.



The aquifer system in the northern District has two major

facets: the sandy, water-table aquifer and the limestone

Floridan Aquifer. The two are separated by a clay layer

which varies in thickness. Where this layer is thin,

leaky or altogether abset, water moves more readily into

the Floridan aquifer from the water table aquifer. In

these areas, the greatest amount of recharge takes place.

In the southern part of the District, the aquifer system

tends to be more complex. Here, the Floridan Aquifer consists

of several types of limestone in layers of various thickness

and water transmitting characteristics. These limestone zones

are separated by clay layers with low-water transmitting

characteristics. Consequently, recharge to the lower limestone

layers is more limited than it is in the northern part of the


Despite the structural differences of the hydrologic system

within the District, it nevertheless operates in the same

manner. A certain amount of rainfall is immediately absorbed

by the land surface. This amount -- which is really only a

very small percentage -- is the amount which enters the

ground water part of the hydrologic system. It filters

through the surficial sand and clay layers very slowly till

it reaches and eventually enters the Floridan aquifer. From

there it moves even more slowly toward discharge points in

springs or the Gulf.

The water which is not absorbed by the ground is either

_1 ~_ r ~

lost to evaporation, transpiration or to overland flow

called runoff, which drains into the nearest low area -- a

swamp, lake, stream, sink, or the Gulf. Most of this

water eventually evaporates or flows into the Gulf, although

a small portion filters into the aquifer and the ground water


Determining just how much water really enters the ground

water system, and just how much of that is available for

man's use, requires some fairly complex scientific thought.

The amount of water annually available for man's use is

referred to today as the "water crop" or the "water budget".

As an accepted theory, it's not really that new. Referring

to it by many different names, scientists have been working

with it for decades. For instance, as early as 1920 the

concept for determining this amount -- referred to then as

"safe yield" -- was used in a United States Geological

Survey technical paper. In that year, 0. E. Meinzer, a

scientist with the Survey, published his paper "Quantitative

Methods of Estimating Ground Water Supplies." He defined

safe yield as: "the rate at which ground water can be

withdrawn year after year without depleting the supply."

Meinzer's definition is based on ideas very similar to

today's concept of water crop -- the amount of water

annually available for man's use.

"Water Crop," referred to as part of the "water balance"

concept, was first used at the District shortly after It

a I __

became a regulatory agency in 1969. Another USGS paper,

published in 1970 as part of the District's cooperative

program with the Survey, entitled "General Hydrology of

the Middle Gulf Area, Florida" refers to "the long term

availability of water, that is the amount of water that

can be developed. ."

But the water crop concept as a tool for water management

and regulation did not come into use at the District until

late 1974. At that time the District was involved in

establishing a code of rules and regulations to assure the

protection of the water resources as required by Chapter

373 of the Florida Statutes. Among other requisites, Ihe

District was to establish #minimum flow2A i-

.water .so. in _tha i _** That is, for e19 streamswerm(
"/ f L" *o 4e _
riversbtpmount of flow4wast be established such that

any further withdrawal ~f~ would be significantly

harmful to the water resources or the ecology of the area.

i- n .... n n... +^ -wi n itr h,.. ... /

minimum level was to be the level of ground water in an

aquifer and the level of surface water at which further

withdrawals would be significantly harmful to-the water

resources of the area.

To establish these levels, the statute directed the District

to use "the best information available." Accordingly, the

water crop concept came into its own.


0 ,, 1 i1 0 1@1. .. 0 ..1 ,

The water crop -- the amount of water anby available for

man's use -- is defined as precipitation less evapotranspiration.

That is, the total water crop for a given area is equal to

the amount of an lI precipitation after the processes of

evaporation and transpiration have taken place. How the

concept actually works is relatively easy to understand if

you compare it to a checking account.

In a checking account, you deposit cas and write checks on
the deposited amount.4 Hopefully, your withdrawals -- checks --

will not total more than theAdeposited amount. The same is

true with the water crop account. The deposit is equal to

the total amount of rainfall less what's lost to evaporation,

transpiration and runoff. If more water is withdrawn from

the aquifer than Nature puts into it, the water account will

Abe operating "in the red"., If that continues for any length
of time, it could result in a serious water situation.

'V BE. his could prove particularly seriously the District

is a hydrologic unit -- a complete entity unto iself. Its

boundaries were established on natural water shed lines, so

there is no appreciable ground or surface water inflow from

areas outside the District. Consequently, the only source

we have of fresh water is rainfall. Of that "income" a

great percentage is lost to runoff and to evapotranspiration.

Only a small portion is allotted to storage in the hydrologic

system -- and it is this stored amount that is tapped by

ground-water pumpage.


I~ I -

oI i @ -i '-a" ; -

Research and investigations conducted by the USGS and

the District staff have shown that in a typical year,

on a District-wide average, approximately 52 inches of

rain falls within our boundaries. Studies indicate that

of this total, 39 inches are lost to evapotranspiration.

The remaining 13 inches become runoff. This is the amount

of water that flows as either ground or surface water

into District rivers and streams and eventually to the

Gulf of Mexico.

Based on the water crop equation (P=Et + r), precipitation (P)

equals evapotranspiration (Et) plus runoff (R) -- this 13

inches of rain is the total potential water crop available

for man's use within the District. That means that a maximum

of about 2.3 trillion gallons of water is available annually

within the District.

If we then divide the total District water crop by its

10,000 square mile area, we find that a single square mile

of land has an annual water crop of about 233-billion gallons,

or a daily water crop of 640,000 gallons. This amounts to'mis a

1,000 gallons an acre each day.

Although this may seem like a lot of water, and assurredly,

there are many, many acres whose water crop is virtually

untouched, there are more and more places where water use

exceeds the water crop of the acreage involved.


- 5-

This is what the District's program of Consumptive Use

Permitting is all about.

Unlike most other natural resources, water is not necessarily

destroyed by use. While coal and oil, for example, can only

be burned once, water can be used, returned to a river, lake

or aquifer, and then re-used again and again. Nature does

this constantly through the hydrologic cycle.

Man simulates this natural re-use in many ways. For instance

a family pumps water from the ground, uses it in their home,

and drains it into a septic tank. From there, it percolates

back into the aquifer and rejoins the natural system. This

use 'is considered non-consumptive because virtually no water

is removed from the site of pumpage, and none is lost to


On the other hand, if a municipal well field pumps water

from the ground, pipes it several miles away to individual

homes, businesses or water systems and then -- through a city

sewerage system -- dumps it into the Gulf or Bay, the use

is totally consumptive.

The difference between consumptive and non-consumptive use

of water, then, is whether it can be re-used by others. If

it is lost to evaporation or transpiration, if it is chemically

polluted, if it is dumped into salty water, it becomes useless

as fresh-water. That makes its use consumptive. If the


_I ri

water flows back into the aquifer or is somehow retained

after its use, the water use is non-consumptive.

It is, of course, physically possible to "spend" more water

than Nature puts into the aquifer without immediately obvious

effects -- just as it's possible for an individual with

credit cards to spend more than he earns during any particular

year. In fact, the massive Floridan Aquifer acts much like a

savings account. It can be drawn down to a limited extent

during dry months -- and even dry years, if necessary -- as

long as comparable "deposits" are made during rainy months

and wet years. But constantly or extensively exceeding the

land's water crop -- called mining of the resource -- can

result in substantial adverse effects. Inevitably such

mining will upset the hydrologic balance of nature, the

delicate equilibrium between salt and fresh water and between

ground and surface water.

The hazards of upsetting this delicate balance are great.

First, as the water level in the aquifer begins to drop,

small domestic wells would gradually become less effective.

And because the water would have to be pumped from a greater

depth, more power would be required to lift less water.

Larger wells would remain functional for a longer period of

time, but only with expensive modifications -- and eventually

they too could go "dry."

Surface waters would begin to show the effects of the imbalance

too. As the aquifer level dropped, the difference in pressures

between the artesian and water table aquifers would increase

Surface water in lakes and streams would flow downward

to "fill the vacuum." The effect? Lake levels would drop,

vegetation would be placed in stress conditions, rivers

would be reduced to creeks and creeks to dry runs.

But perhaps the most serious consequence of mining the resource

is that eventually salt water would find its way into the

fresh water, both above and below ground level. Because

Florida is a peninsula, and becauseof its geologic formations,

the threat of salt-water encroachment is an ever present

problem. All along the coastline, the fresh water of'the

Floridan Aquifer meets the salt water of the Gulf and the

Atlantic. Salt water also underlies the Floridan Aquifer at

various depths through the peninsula. This salt water is

under constant pressure from the Gulf to rise to mean sea

level. It is only the counter-pressure from the fresh waters
in the portion of the Floridan Aquifer above sea level which

prevents that from happening. This fresh water "bubble" is

like an iceberg. If you chip off part of the "top," the

"bottom" begins to rise. If you keep chipping way, it is

soon gone.

If we begin massive mining of the water resource, thereby

reducing the pressure in the aquifer, the eventual result

would be massive salt-water intrusion. f-tJ ep wells
would go salty. Cities and counties would be forced to

switch to an expensive desalination process to supply water

to their residents. MIgqOettrus growers, farmers, ranchers


_~__ __ _____Y

and nurserymen would face a difficult and necessarily expensive

dilemma: irrigate with brackish water; pay for desalted

water; move their operation; or go out of business.

These are the reasons the District Governing Board regulates

the amount of water that can be withdrawn from the aquifer.

When the Board began its Consumptive Use Plan, no records

were available to establish with any degree of assurance how

much water was actually being used. In additi n, the law

gave all existing users ff urY, 7, bc, h

mS.a.p... So it will be several months before the District

will have an accurate inventory of the total amount of

water being used. In the meantime, applications keep coming

in for new or additional uses. Consequently, the District's

information on water use is continually being refined.

The Board has established the Consumptive Use rule so that all

applicants will know the yard stick being applied on a District-

wide basis. If everyone were to take his exact pro rata share of

the water crop, it would average 365,000 gallons per year per

acre. For the health, welfare, and best interests of the

public throughout the District, as well as for the protection

of the water resource, that 365,000 gallon annual total

water crop should not be exceeded. Applicants who desire

to withdraw more than this pro rata share must be prepared

to establish that the proposed use is for a reasonable,

beneficial purpose, that it will not interfere with any

presently existing legal use, and is consistent with the

public interest.



......... ...... .. ....... .' Elm

It must be remembered, however, that the water crop concept
is not in-and-of-itself an absolute rule or regulation of

the District. The concept is a water management tool, and
is used by the staff and the Board in determining the

appropriateness of a request for large-volume water use.
It is used as a guideline, and as such represents the
best information presently available for establishing the

total amount of water available, and t eAreguoa o level s4- a

a-b- ke cIt e a A Jas'r protecting the
public interest and the resource itself,.*aA"tis continually
being refined.

Using the average water crop of 1,000 gallons per day per
acre as a basic guideline, coupled with an understanding of
the hydrologic system and cycle, the Board and its staff can
determine the average rate at which water can be pumped

from a given area over a long period of time without creating.

adverse effects.

In this manner, the water crop remains a tool that is both
flexible enough to work with special types of water use

problems, public-supply well fields such as those involved
with agriculture and industry, and is strong enough to aid
the Board in determining which uses will "obtain the most
beneficial use of the water resources of the State and .
interests of the water users affected."


I I` 7

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