PUB00070

• Year: 1998
• Title: Ground Water and Surface Water A Single Resource U.S. Geological Survey Circular 1139
• CWCB Section: Interstate & Federal
• Author: T.C. Winter, J.W. Harvey, O.L. Franke, W.M. Alley
• Description: Overview of current understandimg of interaction of ground water and surface water in terms of quality and quantity
• Publications - Doc Type: Historical

p

Effects of Pesticide Application to
Agricultural Lands on the Quality of
Ground Water and Surface Water

Pesticide contamination of ground water and surface
water has become a major environmental issue. Recent
studies indicate that pesticides applied to cropland can
contaminate the underlying ground water and then move
along ground-water flow paths to surface water. In addition,
as indicated by the following examples, movement of these
pesticides between surface water and ground water can be
dynamic in response to factors such as bank storage during
periods of high runoff and ground-water withdrawals.
A study of the sources of atrazine, a widely used
herbicide detected in the Cedar River and its associated
alluvial aquifer in Iowa, indicated that ground water was the
major source of atrazine in the river during base-flow condi-
tions. In addition, during periods of high streamflow, surface
water containing high concentrations of atrazine moved
into the bank sediments and alluvial aquifer, then slowly
discharged back to the river as the river level declined.
Reversals of flow related to bank storage were documented
using data for three sampling periods (Figure P-l). The first
sampling (Figure P-l A) was before atrazine was applied to
cropland, when concentrations in the river and aquifer were
relatively low. The second sampling (Figure P-1 B) was after
atrazine was applied to cropland upstream. High streamflow
at this time caused the river stage to peak almost 6 feet above
its base-flow level. which caused the herbicide to move with
the river water into the aquifer. By the third sampling date
(Figure P-l C), the hydraulic gradient between the river
and the alluvial aquifer had reversed again, and atrazine-
contaminated water discharged back into the river.

Cedar River, Iowa. (Photograph by
Douglas Schnoebelen.)

A
, ,
690 ~~
..-
f- 680 ,-,'"
w
w
~ 670

Sampling period February 20 to 22

<:
ui 660
o
~ 650
~
-l640
'"

Sand
... Water table
--- --------~---------:--------~o~i---
Sand ~g3
.- .~

0.3

0.1

0.2
0.1

'*

Glacial till

630

B

Sampling period March 20 to 22

690

, ,
~~
ail:
(0.51)
o.

I- 680
w
w
LL 670
<:
u.i 660
o
~ 650
~
<i. 640

Glacial till

630
C
690 , ,
{5~
f- 680 ..-
w ,-,'"
w (0.21
~ 670
<: 0.'
ui 660
0
:J 650
f-
~
~ 640
'"

Sampling period April 3 to 5

Glacial till

630
VERTICAL EXAGGERATION X 4
DATUM IS SEA LEVEL

100
,

200 FEET

o

EXPLANATION
-0.1- Line of equal atrazine concentration,
in micrograms per liter

. Well location

\ Direction of
(0.21) Concentration of atrazine in river at time ground-water
of sampling, in micrograms per liter flow

Figure P-1. Concentrations of atrazine increased in the
Cedar River in Iowa following applications of the chemical
on agricultural areas upstream from a study site. During high
streamflow (B), the contaminated river water moved into the
alluvial aquifer as bank storage, contaminating ground water.
After the river level declined (C), part of the contaminated
ground water returned to the river. (Modified from Squillace,
P.J., Thurman, E.M., and Furlong, E. T., 1993, Groundwater
as a nonpoint source of atrazine and deethyfatrazine in a river
during base flow conditions: Water Resources Research,
v. 29, no. 6, p. 1719-t729.)

64