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UNIVERSITY OF CALIFORNIA AGRICULTURAL EXTENSION SERVICE

SANTA BARBARA COUNTY

DRA.INAGE CONDITIONS IN THE GUADALUPE AREA By Harwood L*

Hall^and

James N<,

Luthin^

SUMMARY

- This field study shows that a

drainage problem exists west of State Highway

#1

west of Guadalupe

- Only small local areas would bene¬

fit by immediate drainage instal¬

lations ^- a series of wet years could change this picture

- Observations at Key points will

be continued

- Saline accumulations occur in some small areas

- Salinity may increase - this should be considered _{if poor} germination

or plant growth is encountered

- The water table referred to in this

report concerns only ground water which because of impaired drainage

lies just below the gro\md surface.

It is not to be confused with the underground water from which water for irrigation purposes is obtained.

Farm Advisor, Santa Barbara, California Asst. Irrigationist, Exp. Sta,, Davis

The high water table in the lower Santa Maria Valley, west of Guadalupe,

is generally known. Many old-timers tell of reaching water when digging post

holes. Some farmers in the area have experienced poor germination and growth

in certain areas. In general, maximum production is not reached on many of

the crops grown in this region.

In September,

19^1,

it was decided that more factual information should be obtained on water table conditions and the physical condition of the soil.

A series of 2$ observation wells were dug in the area. The location of these

wells is indicated on Figure 1. These wells were ten feet deep and were cased

with 2-inch perforated pipe. Water table readings were taken monthly starting

in October,

195l»

A compilation of all of the data obtained from the observation wells in the Guadalupe area indicates that the average height of the water table dur¬

ing the period October 12,

19^1,

to December 11,

1953,

was

3.96

feet below the ground surface. This figure is not as meaningful as it might appear to be

since some of the observation wells were purposely located in depressions and

in natural drainage channels where the water table is known to be high. How¬

ever, the areal extent of the high water table at these locations is not great.

For example, well

G-i| (see map)

is located in a natural drainage way which is

about 6 feet below the prevailing land surface. Well

G-5

is located adjacent

to a surface runoff canal and this probably accounts for the high readings usually obtained in this well. Well G-8 is also located in a natural drainage

channel which is about 5 feet below the prevailing ground surface. Well G-7

is also located in a low spot. Most of the other wells are located in areas

representative of the surrounding areas. If we omit the readings obtained ^on

wells

G-U, -5,

-7,

-8,

-23, and

-25 (both

-23 and -25 are in drainage

channels),

the average depth to water becomes

1|.82

feet.

(For

levels, see Table 3, pages 10 and 11).

A look at the acconpanying map

(opposite page)

shows both the contours

of the ground, the natural surface drainage, and the contour

(levels)

of the ground water being studiedo The movement of the ground water is usually at right angles to the water contours« The location of these contours were de¬

termined by surveying the elevations of the measuring points of each well

from which readings were taken.

Several interesting observations may be made from these ground water

contours. In the first place the water contours follow closely the general direction of the surface contours, there being very little crossing or meet¬

ing of contour lines. A second point of interest is that the water contours

show a slight ridge of high water table down the center of the irrigated

area. This presumably, has been caused by seepage of excess irrigation water.

The relatively close interval between the

UO

and 50 foot water levels indicates that the slope of the ground water is steep in this area. This condition can be explained either by the fact that there is a more imper¬

vious soil layer at this point or that here is a greater contribution to the water table in this area.

In general the water table approaches the ground surface as you pro¬

ceed west from

Guadalupe.

In the first mile west of Highway

#1 (which

runs north and south through

Guadalupe),

the average depth to the water table is greater than ^ feet and therefore causes no pai*ticular problem with the pos¬

sible exception of a few local areas along drainage ways. In the second

mile west of Highway

#1,

the water table is from 3 to 5 feet below the ground surface and is definitely a problem in some areas.

GUADA LUP E

SO- SO—

,20-'

Hi

23

o .2 4

SCALE

.6 .8

- MILES IjO

GUADALUPE DRAINAGE STUDY

GROUND SURFACE CONTOURS WATER TABLE CONTOURS

SURFACE DRAINAGE CHANNELS- OB SERVAT! ON WELLS ©

SALINITY SAMPLES X

In the mainJ the water table is highest in the area lying along the Guadalupe-Beach Roado One area in particular, lying north of the Guadalupe- Beach Road and about 1<,8 miles west of Guadalupe, has a definite accumula¬

tion of salt on the soil surface<. This saline area is several acres in

extent•

A low-lying area bracketed by wells

G-I6,

-17, and

-I8

was tile drained

in the past

(about 191^).

Most of the tiles are working satisfactorily and

no drainage problem exists at present,,

s

In the area 2-3 miles west of Highway

#1,

the average depth to the

water table is about 3 feet during the period of observationo It is in this

area that the greatest possibility of crop reduction due to high water table existso The lower-lying lands where wells G-22 and -23 are located are def¬

initely limited to crops which will tolerate excessively wet conditions such

as pasture grasses.

Over the Guadalupe area as a whole, the water table is somewhat higher during the rainy season than it is during the summero However, the seasonal

variation is not great.

The question naturally arises as to the cause of the high water table condition in the Guadalupe area. The most likely possibility is the pre¬

sence of clay layers which restrict the downward movement of water® Both

precipitation and irrigation water contribute to the drainage situation.

The Salinity Situation ^- In arid regions the usual consequence of a

high water table is the accumulation of salines or salts on the soil sur¬

face. Soil samples were collected at representative locations in the

Guadalupe area. Samples were taken of the surface 6 _{inches, 12} - 18 inches,

and 18 ^- 36 inches. Gup Tests ^were made to determine the percent salt pre¬

sent, On the two sampling locations that showed presence of sufficient salt

-6-

to influence plant growth, detailed analyses were made of the saturation

extracts to determine the chemical composition of the salt<.

In general no salinity problem exists in the Guadalupe area with the exception of a small area of a few acres located 1.8 miles west of Guadalupe

and north of the Guadalupe-Beach Road. Slight salt accumulations ^were also noted at other locations. Although the salinity problem is confined to

small local areas at present, it is possible that the problem might become

more general if the water table stays within 2 to 3 feet of the soil surface

for long periods of time.

Where the salines have accumulated on the soil surface to a harmful

degree, tile drainage systems should be installed and leaching practiced.

Table 1

Soil Salinity Tests ^■— Guadalupe Area Sampling

Location

Resistance (Soil

cup)

0 » 6" 6 - 18" 18 - 36"

Soil Texture

1 7iiO 1260 820 Sandy loam

2

3

370 Furrow

235

UiiO

Bed

TH2

300 Loam

Clay loam

k _{360 Clay}

5 139 i5i 160 Clay loam

6 225 Loam

7 78 139 100 Loam

8 1420 305 310 ^Fine sandy

loam

9 220 200 200 Clay

Per Cent Salt in Samples Indicating Salt

5 o23 ^.21 .20

7 .kh .23 .35

Extract Analysis of

5

and 7 express as

me/liter

K X

105

Na Ga Mg K ^Total

350.6 7.05 31.05 114.33 1.02 53.1^5 1976.14 135.82 30.20 92.50 2.U6 260.98

-7-

Water Penetration ^— The rate at iwhich water enters a soil is influenced by several factors. Soil salinity is an important consideration# Where sodi¬

um is present in the soil in excess, poor water penetration is frequently the

result# Soil compaction by tillage iii5)lements is another factor causing poor penetration of irrigation water.

Several tests of the rate of water penetration

(called

infiltration

rate)

were made in the Guadalupe area# The tests were made with cylinders

6

inches

in diameter and 18 inches long placed on the soil surface# The cylinders were driven about 2 to 3 inches into the soil and then filled with water# The height of the water in the cylinders was measured with a hook gauge# After 2

to 3 hours another reading of the water level in the cylinders was made# From

these readings the infiltration rates were calculated#

Of particular interest are the readings taken in a young field of cauli¬

flower# It is customary in the culture of cauliflower to place the irriga¬

tion furrow adjacent to the cauliflower seedlings# When the plants become large enough, the furrow is moved to the center of the row# This operation

involves several passes of the tractor wheels down the rows# All of these operations are performed in soil that is fairly wet# In order to study the effect of this operation on the soil structure, infiltration tests were made

in the beds and in the furrows# The tests clearly indicate the compacting effect of the tractor wheels in the soil# The infiltration rate in the fur¬

rows was

1/20

that in the beds#

The results of all of the infiltration tests made indicate that water

penetration is probably not a problem in most of the Guadalupe area# Some

local problems arise in vegetable culture where the soil is cultivated while

it is wet, but in general the infiltration rate is high#

-8-

Table 2

Results of Infiltration Tests in Guadalupe Area

Test Location Infiltration Rate Crop ^{Soil Remarks}

h

Inches per hour Av, " 2o7

in/hour

Avo =068

in/hour

Sugar

beets

Sugar

beets

ao Avo =

b» Av. =

Av. =!

more than 8

in/hr

Cauli¬

flower

,3ii6

in/hour

..22

in/hour

Avo = 3«.23

in/hour

Avo 2.i|0

in/hour

Av. =3.16

in/hour

Arti¬

chokes

Lettuce

Sugar beets

Sugar

beets

Yolo Sandy-

loam

Dublin

clay loam

Yolo fine sandy loam

Dublin

clay

Dublin

clay adobe

Dublin fine

sandy loam

Dublin

clay

In bed. Soil

was weto Saturated at 3 feet

In furrows

Soil is dry.

Bed.

Furrow

Soil irri¬

gated re¬

cently

Soil sur¬

face is

dry

Furrow and bed

•if -M- * * * *

-9-

Table 3

DISTANCE FROM GROUMD GmDALRPE

SURFACE TO WATER INVESTIGATION

TABLE

Well No.

Elev. of Ground Surface

Oct. 12

1951

Jan. 10

1952

April 1952

July 3 1952

G 1 70.3 5.66

5o5i|

ii.26 ^Mud

G 2 72.0 7.65 6.98

5.81;

G 3 78.1 6.81 NR 6.16 5.19

G 1; 71.li 1.13 loii3 1.15 2,78

G ^ 77.S ^NR 3.69 3.11i 3.19

G 6 79.2 7.96 NR 7.65 Dry

G 7 58. li 2.63 li.92 2.96 6.51

G 8 59.1 6.31 0.7U 0.39 2.03

G 9 67.0 _Dry NR 6.69 6.81;

G 10 58.3 ^NR 2.30 3.92 1;.90

G 11 58.8 ^NR

ii.52 I10O7

^6.06

G 12 55.2 NR 2.53 3.58 ^6.18

G 13

57.6

NR NR 6.65 ^6.06

G Ik

1*9.U

NR 0.77 2.57 1;.98

G 15

1*7.8

^NR _0.58 2.91 5.90

G 16 1*0.8 ^NR NR 3.20

3.53

G 17

1*1*.1

NR NR 2.89 1;.60

G 18 53.0 _Dry ^NR lio5o ^Mud

G 19 1*1*.8 3.72 ^0.11 1.30 2o02

G 20 35.6 3.6U 1.62 2.87 2.i;6

G 21 36.1 i;.U5 0.U9 1.37 3.28

G 22 27.5 i;o3ii 0.90 2.69 3.91

G 23 22.2 2.15 Ooh3 0.77 2.17

G 25 78.7 ^NR 1.53 2.16 2.68

■J^NR - No Record

-10-

Table

^

Continued

Oct. 3 1932

Jan, 8 19^3

March 31 1953

July 1 1953

Oct. 2

1953

Dec, 11 1953

Dry li.6^ ^2.18 5.37 ^NR 6.91

7.23

i;.82 5.17 i;.29 6.38 6,51

6.6U 5.98 6.71 ^6.68 6,U5

2.It?

0.63 2.19 ^2.18 1.1;7 2,76

3.33 3.32 3.2J4 l;.5l

3.56

I1.060

7.1t3 7.00 ^{REMOVED -}

6.27 3.29 i;.36 3.93 5.63 ^6,02

1.23

0,]i3 1.53 1.85 1.96 1.57

7.93 7.15 ^{REMOVED -}

3.17 2o61i. U.69 5.55 1;.98 5.86

lt.6l

3.02 5.36 3.56 l;.7l; 5.85

6.39 ^2o82 5.05 6,31; ^6,10 6,51;

3.03 l;o80 ^{REMOVED -}

3.35 1,51 3.12 1;.13 3.82 1;.75

6.20 3.19 2.90 1,61 2.29 6.10

3.70 2,81 l.hl 3.16 ^2,86 3.00

3.31 2.7li 3.76 6,37 7.15 5.31

Mud U.U6 ^{REMOVED -}

1.83 0.62 3.OU 2,98 3.20 3.12

2oii7 ^2,22 2,i|lj. 3.71;

l;.7l;

5.16

2it6h 0,98 2.53 3.63 _Dry 1;.25

3.37 1.52 3.77 3.37 i;.90 3.55

2ol7 0,18 1.51; 2,53 2,91; 2,i;5

3.68 2.1;7 3.26 U.ll 1;,68 1;.65

-11-

Thanks to the omiers and growers upon whose land these wells were located.

The work done by the University of California Department of Irrigation

on this project adds greatly to our store of knowledge and information

which is invaluable to crop production.

This project report is based on Santa Barbara County Agricultural Extension Service project

#^8 (state #3955)•

For further information, contact

Farm Advisors' Office

Santa Barbara P.O. Box 126

203 Federal Bldg, 125 W. Church St Santa Maria PoGo Box 195