Long-Term Hydrologic Monitoring Protocol for Coastal Ecosystems

Open-File Report 02-497

By TIMOTHY D. McCOBB AND PETER K. WEISKEL

PREFACE

Overview of Long-Term Monitoring Program

The Cape Cod National Seashore serves as a National Park Service prototype-monitoring park for the Atlantic and Gulf Coast biogeographic region. The U.S. Geological Survey, in cooperation with the National Park Service, is charged with designing and testing monitoring protocols for implementation at the Cape Cod National Seashore. It is expected that many of the protocols will have direct application at other coastal park units, as well as U.S. Fish and Wildlife Service coastal refuges, within the biogeographic region. The Long-term Coastal Ecosystem Monitoring Program at the Cape Cod National Seashore will rely upon numerous protocols that are relevant to the major ecosystem types (Estuaries and Salt Marshes, Barrier Islands/Spits/Dunes, Ponds and Freshwater Wetlands, Coastal Uplands). The hydrologic monitoring protocol is associated with all of these ecosystem types. The overall monitoring program is designed so that all of the protocols are interrelated. Roman and Barrett (1999)present a conceptual description of the entire monitoring program.

Protocol Organization

To maintain consistency among the various monitoring protocols, each protocol is organized as follows. PART ONE of the protocol details the objectives of the monitoring protocol and provides justification for the recommended sampling program. The relevant literature and data collected during the protocol development phase of the project are used to illustrate particular sampling designs, sampling methods, or data-analysis techniques. For example, PART ONE describes the objectives of a water-level monitoring program and provides the justification as to why certain monitoring wells and the measurement schedule were selected. PART TWO is a description of the field, data-analysis, and data-management aspects of the protocol. For example, PART TWO explains the step-by-step procedure for measuring a ground-water level in a monitoring well.

EXECUTIVE SUMMARY

Long-term monitoring of hydrologic change using a standard data-collection protocol is essential for the effective management of terrestrial, aquatic, and estuarine ecosystems in the coastal park environment. This study develops a consistent protocol for monitoring changes in ground-water levels, pond levels, and stream discharge using methods and techniques established by the U.S. Geological Survey for use in the Long-term Coastal Monitoring Program at the Cape Cod National Seashore. The protocol establishes a hydrologic sampling network in the four ground-water-flow cells in the Seashore area, and provides justification for the measurement methods selected and for the spatial and temporal sampling frequency. Data collected during the first year of monitoring are included in this report; common hydrologic analyses such as hydrographs for ground-water and pond levels, and rating curves between stream stage and discharge for streamflow, are presented for selected sites. Long-term hydrologic monitoring at the Seashore will aid in interpretation of the findings of other monitoring programs. Developing and initiating long-term hydrologic monitoring programs will provide a better understanding of effects of natural and human-induced change at both the local and global scales on coastal water resources in park units.

Preface

Executive Summary

Acknowledgments

PART ONE - Protocol Background and Justification

Introduction

Monitoring Questions: Specific Hydrologic Trends and Issues to Address.

Sea-Level Rise

Climatic Change

Urbanization

Sampling Methods

Ground Water

Streamflow

Ponds, Lakes, and Seasonal Wetlands

PART TWO - Specific Protocols Followed for the Cape Cod National Seashore

Ground-Water-Level Monitoring

General Well Installation Procedures

Determination of Well Measuring-Point Elevation

Water-Level Measurements

Specific Data Collected at Each Well Site

Streamflow Measurements

Reference-Point Establishment and Leveling

Stage and Discharge Measurements

Water-Level Measurements in Ponds and Seasonal Wetlands

Siphon-Gage Installation

Reference-Point and Pond Leveling

Measurement Procedure for Siphon Gages

Data Management

Data Requirements and Storage

Data-Analysis Techniques

Ground Water, Ponds, and Seasonal Wetlands

Streamflow

Equipment Lists

Ground-Water Equipment and Supplies

Streamflow-Measurement Equipment

Pond and Seasonal Wetlands Measurement Equipment

References Cited

Appendices

FIGURES

1. Hydrologic-monitoring-protocol area with the Lower Cape Cod ground-water-flow cells

2. An example of how agents of hydrologic change can stress the hydrologic system at the Cape Cod National Seashore and cause a variety of ecosystem responses

3. Annual mean sea-level rise at the Boston, Massachusetts tide gage

4. Long-term hydrograph from observation well TSW 1-0068 near the coast and near a water-supply well in Truro, Mass.

5. Model calculated water-table altitude and position of the freshwater-saltwater interface at observation well TSW 89 for average recharge conditions and for simulation of a 5-year drought and 1989 pumping rates, Cape Cod, Massachusetts

6. Selected long-term observation-well network for monthly water-level monitoring as part of the Long-Term Coastal Ecosystem Monitoring Program at Cape Cod National Seashore

7. Photograph of a rotary drilling rig (CME-75) with 6-in-OD hollow-stem augers used to install 2-in-diameter observation wells

8. Photograph of a hydrologic technician measuring water level in an observation well. Protective casing, 2-in. PVC well, locking cap, measuring point, and electric measuring tape shown

9. Graphs showing different types of water-level fluctuations in three observation wells and a comparison between the graphs plotted for daily, weekly, and monthly water levels in the same observation well

10. Selected sites for long-term monthly streamflow monitoring through first year of monitoring as part of the Long-Term Coastal Ecosystem Monitoring Program at Cape Cod National Seashore

11. Recommended stream-gaging sites for long-term monthly monitoring as part of the Long-Term Coastal Ecosystem Monitoring Program at the Cape Cod National Seashore on the basis of data review and site reconnaissance after first year of operation

12. Schematic diagram of the velocity-area method for determining stream discharge

13. Photographs of stream-gaging measurement equipment includes: (A) Type AA current meter with headset and stopwatch, (B) Pygmy current meter with automated digitizer, (C) Type AA current meter on a wading rod, and (D) a Pygmy current meter on a wading rod

14. Selected ponds for long-term monthly water-level monitoring as part of the Long-Term Coastal Ecosystem Monitoring Program at Cape Cod National Seashore

15. Photographs and schematic diagrams of stage monitoring devices including: (A) staff gage, (B) stilling well, and (C) pressure-transducer system

16. Schematic construction diagram of a siphon gage for monitoring pond levels

17. Comparison of hydraulic-gradient estimations among three ponds over a one-month period (September 1999 to October 1999)

18. Three types of hydrographs for Truro well TSW 89-000028 showing (A) long-term monthly water-level measurements over a period of nearly 40 years; (B) comparison between water levels measured during the protocol measurement period and historical monthly high, average, and low water-level measurements; and (C) statistical distribution (box plots) of water levels for each month for the period of record

19. Current-conditions hydrographs for four protocol wells from different Lower Cape Cod ground-water-flow cells

20. An example of a water-table map for an area near the top of the Chequesset flow cell for two different measurement dates

21. Schematic diagram of a three-point triangulation for hydraulic-gradient analysis

22. An example of a stage-discharge rating curve for the Quashnet River stream-gaging station (011058837), Cape Cod, MA, for the protocol measurement period

23. An example of a stage hydrograph for the Herring River stream-gaging station (011058793) near Wellfleet, Mass., Herring Pond, and well WNW 122 near the head of the Herring River for the protocol-monitoring period

24. Flow-duration curve of daily mean discharge at the Quashnet River stream-gaging station (011058837) on western Cape Cod for water years 1989-2000

TABLES

1. General criteria for selection of observation monitoring well sites

2. Specific criteria used for choosing sites for observation wells at Cape Cod National Seashore

3. Final well network selected for long-term hydrologic monitoring at Cape Cod National Seashore

4. Summary of well-construction methods

5. Observed monthly water-table altitudes for the long-term Cape Cod National Seashore network, February 23, 1999 - January 24, 2000

6. Range in water-table elevations in protocol wells at selected locations by flow cell

7. Specific site criteria for an ideal stream-gaging site

8. Stream-gaging stations selected for long-term monitoring at Cape Cod National Seashore: (a) Four sites measured during first year of monitoring program and (b) Final eight sites recommended for long-term monitoring program

9. Methods for measuring stage (recording and non-recording)

10. Measured streamflow for the first year of monitoring as part of the Long-Term Coastal Ecosystem Monitoring Program at the Cape Cod National Seashore, February 23, 1999 - January 24, 2000

11. Configuration and recommended velocity and depth ranges for U.S. Geological Survey current meters

12. Final siphon-gage network selected for long-term pond level monitoring at Cape Cod National Seashore

13. Comparison of pond-level surveying and pond levels determined by siphon gage at selected Cape Cod National Seashore ponds

14. Observed monthly pond-level elevations for the long-term Cape Cod National Seashore network, February 23, 1999 - January 24, 2000

15. Data to be archived and archive periods

16. Results of horizontal hydraulic-gradient analysis based on water levels measured in wells EGW 52, EGW 51, and EGW 36 for the protocol period

17. Required equipment for site clearing, monitoring-well installation, reference-point leveling, and water-level measurements

18. Required equipment for conducting streamflow monitoring and determining reference-point elevation

19. Required equipment for installing, operating, and maintaining of a siphon gage, and determining reference-point elevation

LIST OF APPENDICES

1a. Example of a monitoring-well construction log

1b. Monitoring-well construction log for well TSW 257-0035

2a. Example field sheet for a well-site sketch map

2b. Sketched location map for well TSW 257-0035

3a. Example of a lithologic-construction log field sheet

3b. Lithologic-construction log for long-term well EGW-36

4a. Example field sheet for leveling of well measuring points and stream-gaging station

4b. Leveling notes from Duck Pond, Wellfleet, Mass.

5a. Example of a water-level measurement field sheet

5b. Water-level measurement field sheet for CACO wells during the month of January 2000

6a. Example of a USGS discharge measurement field sheet

6b. Discharge measurement field sheet from Herring River near Wellfleet, Mass., September 2000

7. Standard rating table No. 2 for AA current meters (6/99)

8. Standard rating table No. 2 for Pygmy current meters (6/99)

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The citation for this report, in USGS format, is as follows:

McCobb, T.D., and Weiskel, P.K., 2003, Long-Term Hydrologic Monitoring Protocol for Coastal Ecosystems: U.S. Geological Survey Open-File Report 02-497, 94 p.

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