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USGS Surface-Water Data for Maryland

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[!] During cold weather, ice effects on stage, groundwater levels, precipitation and water quality parameters at some stream-gaging stations and wells are likely. Data values reported on these pages may be significantly higher or lower than actual values. Adjustment of data for ice effects can only be done after detailed analysis. Users are encouraged to contact this office for more information on specific stream-gaging stations or wells.




(210 sites)

Current conditions at selected sites based on the most recent data from on-site automated recording equipment. Measurements are commonly recorded at a fixed interval of 15- to 60-minutes and transmitted to the USGS every hour. Values may include "Approved" (quality-assured data that may be published) and/or more recent "Provisional" data (of unverified accuracy and subject to revision). Most current data are provisional.

(214 sites)

The same data accessed by the Current Conditions link above but including both active and discontinued sites with data for any part of the period October 1, 2007, through the present. Values may include "Approved" (quality-assured data that may be published) and/or more recent "Provisional" data (of unverified accuracy and subject to revision).

(358 sites)

Summary of all data for each day for the period of record and may represent the daily mean, median, maximum, minimum, and/or other derived value. Values may include "Approved" (quality-assured data that may be published) and/or more recent "Provisional" data (of unverified accuracy and subject to revision). Example.

Statistics
(333 sites)

Statistics are computed from approved daily mean data at each site. These links provide summaries of approved historical daily values for daily, monthly, and annual (water year or calendar year) time periods.

(266 sites)

Annual maximum instantaneous peak streamflow and gage height

(585 sites)

Manual measurements of streamflow and gage height. These measurements are used to supplement and (or) verify the accuracy of the automatically recorded observations, as well as to compute streamflow based on gage height.

Introduction

The U.S. Geological Survey's (USGS) National Water Information System (NWIS) is a comprehensive and distributed application that supports the acquisition, processing, and long-term storage of water data. Water Data for the Nation serves as the publicly available portal to a geographically seamless set of much of the water data maintained within NWIS (additional background).

Nationally, USGS surface-water data includes more than 850,000 station years of time-series data that describe stream levels, streamflow (discharge), reservoir and lake levels, surface-water quality, and rainfall. The data are collected by automatic recorders and manual field measurements at installations across the Nation.

Data are collected by field personnel or relayed through telephones or satellites to offices where it is stored and processed. The data relayed through the Geostationary Operational Environmental Satellite (GOES) system are processed automatically in near real time, and in many cases, current data are available online within minutes.

Once a complete day of readings are received from a site, daily summary data are generated and made available online. Annually, the USGS finalizes and publishes the daily data in a series of water-data reports. Approved daily data and peak data are updated annually following publication of the reports.

Tutorial explaining how to perform a surface water retrieval and understand the results