Biological and Environmental Engineering

Soil & Water Research Group

Spatial Variability of Groundwater Soluble Phosphorous on an Alluvial Valley-Fill Aquifer and Connection

to Stream Quality in the Catskill Mountains

Francisco Flores-LopezFrancisco Flores-LopezZachary M. EastonZachary M. Easton

Tammo S. SteenhuisTammo S. Steenhuis

Cornell UniversityBiological and Environmental Engineering

Biological and Environmental Engineering

Soil & Water Research Group

Groundwater monitoring of SRP levels in agricultural fields and connection to stream quality is the major consideration in this study

Objective

To develop a farm-scale groundwater flow model and incorporate data regarding spatial variability of SRP to describe and predict SRP transport

• To identify critical management groundwater areas that may affect the stream SRP concentrations

• To assess the influence of these high risk groundwater areas on stream flow SRP concentrations

Biological and Environmental Engineering

Soil & Water Research Group

Site Layout, Water Samples and Data Analysis

• Soluble Reactive Phosphorous

• Modeling of the Groundwater Modeling of the Groundwater Flow (Visual ModFlow) and Flow (Visual ModFlow) and SRP Tracking Pathlines SRP Tracking Pathlines (MODPATH)(MODPATH)• Steady State ConditionsSteady State Conditions

• Geostatistical Analysis of Geostatistical Analysis of Groundwater SRP – Kriging Groundwater SRP – Kriging Interpolation by SeasonsInterpolation by Seasons

• Relationship between Relationship between Groundwater SRP Spatial Groundwater SRP Spatial Variability and Stream QualityVariability and Stream Quality

• Valley bottom dairy farm in the Valley bottom dairy farm in the Cannonsville Reservoir Cannonsville Reservoir

Watershed Watershed

• 22 Piezometers22 Piezometers• Depths from 0.3 to 1.5 mDepths from 0.3 to 1.5 m• 542 groundwater samples 542 groundwater samples (06/2004 –(06/2004 – 04/2006)04/2006)

• 22 Capacitance probes (Data 22 Capacitance probes (Data Loggers)Loggers)

• 1 hr intervals1 hr intervals

• 4 Stream Sampling Sites4 Stream Sampling Sites• 146 stream water samples 146 stream water samples

• Sampling once every two weeksSampling once every two weeks- base flow conditions -- base flow conditions -

Biological and Environmental Engineering

Soil & Water Research Group

Results –SRP Concentrations (mg L-1)

Season # of Samples Minimum Maximum Mean SE of Mean Skewness

Groundwater

Summer 88 0.009 0.078 0.029 0.005 1.43

Fall 176 0.005 0.193 0.048 0.011 2.25

Winter 130 0.003 0.069 0.028 0.003 1.23

Spring 148 0.010 0.099 0.032 0.005 1.93

Creek B

Summer 42 0.006 0.239 0.035 0.006 4.73

Fall 47 0.002 0.397 0.046 0.011 2.97

Winter 26 0.002 0.161 0.044 0.009 1.47

Spring 31 0.008 0.175 0.024 0.005 4.52

Biological and Environmental Engineering

Soil & Water Research Group

Results – Modeling of Groundwater Flow (ModFlow)

Correlation coefficient for thecalibrated steady state andobserved average water tableheight: r2 = 0.76

Average groundwater tabledepth = 0.6 m

Maximum depth: Summer (0.72 m)

Minimum depth: Spring (0.50 m)

SRP tracking:

- P21 shortest travel distance: 30 m

- P8 longest travel distance : 420 m

- Seven of the 22 piezometers influenced Creek B (P10, P12, P15, P17, P21, P22, and P27)

y = 0.9893x + 3.7491

R2 = 0.7585

365

366

367

368

369

370

371

365 366 367 368 369 370 371

Observed Head (m)

Calc

ula

ted H

ead (m

)

-

Biological and Environmental Engineering

Soil & Water Research Group

Results – Predicted Groundwater SRP Maps at 10-m Cell Size Resolution

Biological and Environmental Engineering

Soil & Water Research Group

Results – Predicted Groundwater SRP and Distance to Streams

Summer

y = 0.0461e-0.0029x

R2 = 0.3388

0.00

0.02

0.04

0.06

0.08

0.10

0 50 100 150 200 250 300 350 400

Travel Distance to Stream (m)

Pre

dic

ted S

RP

(m

g/L

)

1

Spring

y = 0.0427e-0.0023x

R2 = 0.3569

0.00

0.02

0.04

0.06

0.08

0.10

0 50 100 150 200 250 300 350 400

Travel Distance to Stream (m)

Pre

dic

ted S

RP

(m

g/L

)

1

Winter

y = 0.0225e0.0011x

R2 = 0.0697

0.00

0.02

0.04

0.06

0.08

0.10

0 50 100 150 200 250 300 350 400

Travel Distance to Stream (m)

Pre

dic

ted S

RP

(m

g/L

)

1

Fall

y = 0.0794e-0.0038x

R2 = 0.4026

0.00

0.04

0.08

0.12

0.16

0.20

0 50 100 150 200 250 300 350 400

Travel Distance to Stream (m)

Pre

dic

ted S

RP

(m

g/L

)

1

Biological and Environmental Engineering

Soil & Water Research Group

Results – Stream Quality

Sampling Sites

0.0

0.2

0.4

0.6

0.8

1.0

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40

Sorted SRP Concentration (mg/L)

Cum

ula

tive F

requency

B1 B2

B3 B4

0.03

Creek B fed by groundwater [GW & SW not statistically different (p=0.876)]Stream sampling at “base flow” = 75% water samples < 0.03 mg L-1

=> Background groundwater SRP

Biological and Environmental Engineering

Soil & Water Research Group

Conclusions

• We identified critical management groundwater zones where high SRP concentrations may be reaching streams

• Best management practices should be implemented in riparian areas (targeting hydrological pathways) to improve water quality

• Results demonstrate the importance of identifying processes that describe groundwater and stream flow interactions

Biological and Environmental Engineering

Soil & Water Research Group

Thank you !!!