Workplans on Study Design

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The NAWQA program balances the unique assessment requirements of individual study units with a nationally consistent design and data-collection structure that incorporates a multiscale, interdisciplinary approach. Surface- and groundwater studies are conducted at local scales (a few square miles to hundreds of square miles) to study relations between land use and water quality, and at regional scales (thousands of square miles) to investigate the water-quality conditions and issues within a study unit.

An occurrence and distribution assessment is the largest and most important component of the first high-intensity study phase in each study unit. The goal of this assessment is to characterize, in a nationally consistent manner, the broad-scale geographic and seasonal distributions of water-quality conditions in relation to major contaminant sources, land use, and background conditions. The typical surface-water and groundwater monitoring components of the occurrence and distribution assessment are described below. The Delaware River Basin NAWQA study will follow these guidelines.

This document describes the preliminary design for the occurrence and distribution assessment phase of the Delaware River Basin NAWQA study for the years 1999 to 2001. The design focuses on 1) the environmental stratification for the study unit; 2) hydrologic, chemical, and ecological aspects of the surface water network; and 3) sub-unit surveys and land-use survey components of the groundwater network.

A description of the Delaware NAWQA study unit and a discussion of water-quality issues within the basin can be found in our introductory factsheet. Details on the overall design and goals of the NAWQA program can be found at the NAWQA national web site.

Study Design

The study unit design was developed in consultation with our liaison committee, local members of the Hudson (HDSN), Long Island - New Jersey (LINJ), and Lower Susquehanna (LSUS) NAWQA study units, personnel in the different USGS districts with expertise in various water quality disciplines, the NAWQA Regional Hydrologist, and the NAWQA National Synthesis Teams (NST). As a first step the subunits and land uses within the subunits were prioritized so decisions could be made regarding locations for potential fixed sites, sub-unit surveys, and Land Use Surveys. The prioritization was made based upon recommendations of the study-unit liaison committee, USGS personnel from the various districts, and NAWQA NST members. Factors considered during this prioritization include population, land use, recent urbanization, existing studies, and water use within subunits. Results from the retrospective analysis of existing data also helped to focus our work on subunits with the most critical or least understood water quality issues.

As a result of our analysis we have decided to focus much of our work in the Piedmont (2 fixed sites and 1 or 2 groundwater studies) and Coastal Plain Provinces (2 fixed sites) which have extensive urban and agricultural development. Work will also be conducted in the Valley and Ridge Province (2 fixed sites and 1 groundwater study) because of extensive agricultural development in that region. Other surface-water sites in the basin will be studied as part of our synoptic surveys. A groundwater study of the northern glacial valleys of the Appalachian Province is planned to fill data gaps in this region.

The main goal for 1999 will be to collect data to characterize water quality patterns at fixed sites and relate those changes to natural and human factors. This will include establishing our fixed surface-water sampling sites, conducting ecological sampling at the fixed sites, and starting our groundwater surveys. Synoptic surveys in later years will be used to better characterize spatial and temporal patterns observed in the first year of sampling. Bed sediment and tissue work at the fixed sites started in 1998 and additional sites will be sampled in 1999 and 2000.

Environmental Stratification

Many factors that affect the sources, behavior, and effects of contaminants and water-quality conditions are common to most hydrologic systems (although in widely varying degrees of importance). These common natural and human-related factors, such as geology and land use, provide a unifying framework for making comparative assessments of water quality within and among hydrologic systems at a wide range of scales and characteristics in different parts of the Nation. The environmental framework is used to compare and contrast findings on water quality within and among study units in relation to causative factors and, ultimately, to develop inferences about water quality in areas that have not been sampled.

NAWQA study units are initially characterized by stratifying the study area into several major subareas that have relatively homogeneous combinations of natural features and land-use conditions that generally are relevant to surface- and groundwater quality. This general geographic characterization supports the development of initial conceptual models for evaluating study priorities and approaches for study units and national synthesis.

The Delaware NAWQA Study area was subdivided primarily on physiography or ecoregion, then rock type and land use. The surface-water stratification was based on ecoregions and the groundwater stratification was based on physiography. For the most part the physiography and level 3 ecoregions have very similar boundaries in the study unit. However, there is an area of the Northern Appalachian Plateaus and Uplands ecoregion that intrudes into the western portion of the Appalachian Plateaus physiographic province (North Central Appalachians ecoregion).

The secondary stratifier for both surface water and groundwater was rock type (carbonate, clastic, crystalline, and unconsolidated sediments), because each of these rock types can have an effect on water chemistry, ecology, and hydrology. Clastic refers to all silicic sedimentary rock types (conglomerates, sandstones, shales, slates, etc.) and crystalline refers to igneous and highly metamorphosed silicic rocks. The final stratifier was land use (agriculture, forest, urban, and coal mining). The stratification scheme has a total of 5 physiographic provinces, 9 subunits, and 28 land-use subareas. Our initial stratification was presented to our liaison committee in December 1997 and we made modifications in response to their comments and those of the NST. Population and land-use data for each of the strata are presented in the table.