Low Flow Evaluation

Evaluating the effectiveness of the hydrometric network for assessing low flow conditions in Ontario

This Watershed Science Centre project is conducted in co-operation with:

Background

The evolution of the hydrometric network in Ontario has resulted in a strong focus to monitor high flows for flood forecasting programs. A trend to generally-drier conditions in the Province over the last few years has motivated interest in the effectiveness of the network to provide information on low flow conditions. This project, funded by the Ontario Ministry of Natural Resources, has been developed at the Watershed Science Centre, Trent University in response to this interest.

A major objective of the project is determining where additional streamflow gauges (re-activation of discontinued stations, inclusion of local stations not part of the present network as well as new stations) should be established in order to improve our ability to assess low flow conditions, should funding become available. Low flow conditions, based on monthly calculations, are those that are below the minimum average summer month flow. A better understanding of low flow conditions within the Province is essential for assessing their potential influence on water extraction, water quality, and aquatic ecology. Of particular interest is: a) the representativeness of the low flow recorded at a particular gauge of streamflows in the surrounding region [both gauged and ungauged]; and b) the measurement accuracy of low flows. We are assuming that the "surrounding region" will vary depending on the jurisdiction of the survey respondent (i.e. respondents will use Conservation Authority Boundaries or Water Survey of Canada [WSC] Sub-Sub-Basin Boundaries). The representativeness of a gauged basin to other local basins is also being analysed by summarizing and comparing gauged basin characteristics with respect to landcover, soils, and surficial geology within WSC basins.

We ask for your assistance in this endeavour by confirming current information on gauging sites as well as participating in the following survey.

An Excel spreadsheet "LOWFLOW.xls" was forwarded to you by E-mail. The file contains three worksheets (legends at the bottom). The first Excel worksheet titled active gauges is a database of active hydrometric stations in Ontario. This information has been compiled using previously acquired survey data (Dillon, 1996) and data from the WSC's HYDAT database, and is sorted by operator name, conservation authority, and station code. We ask that you examine the accuracy/completeness of the information associated with the gauges that are within your jurisdiction and make appropriate updates/corrections. When updating/correcting information, please use the cell properties to change the shading of the cell to highlight your changes. The survey makes reference to the minimum average summer monthly flow (cms), and these data have been provided in the spreadsheet for many gauging stations. Where applicable, changes should also be made to the decommissioned gauges worksheet within the Excel spreadsheet (e.g. where decommissioned gauges have been recently reactivated).

REFERENCE:

Dillon Consulting Limited, 1996. Rationalization of surface water monitoring stations for flood management and water related resource management. Prepared for The Ontario Ministry of Natural Resources, 138p.

Survey

We have attempted to make this survey as user-friendly as possible by the use of check boxes, drop-down boxes, etc. However, we strongly encourage use of the comment space below the questions if you feel that the response choices are inadequate or if more detailed information is warranted. If you experience any difficulties with this form, please forward the details to ahouse@trentu.ca. You will receive an e-mail verifying that your submission(s) were received.

Your Name:	(required)
Affiliation:	(required)
E-mail	(required)

Part One: Regional Hydrometric Network

Does the current gauge network (only those gauges listed in the spreadsheet) provide an adequate representation of low flow conditions throughout the drainage basins in the surrounding region (i.e. WSC sub-sub-basin or Conservation Authority jurisdiction)?

YES, the current gauge network provides adequate representativeness and can be used to extrapolate to ungauged areas within the surrounding region.

NO, the currently monitored stream flows do not adequately represent low flow conditions within the surrounding region and extrapolation to ungauged areas is limited.

If YES, please skip to the next section on individual gauges.
Go to submit and advance to next section.

How many gauging sites would be required in this region to provide optimal monitoring of low flow conditions and maximize the utility of extrapolation?

New gauging stations.

Reinstating decommissioned WSC gauges.

Incorporating existing, locally-operated gauges currently not in HYDAT.

Please use the Addgauge worksheet in the Excel workbook to provide information for the gauges listed above. Identify whether the gauge is new (N), reinstated (R), or local (L) and provide the WSC station code for decommissioned gauging stations and a code for local gauging stations. Please provide gauge information, flow type, seasonality, access type and unique code if possible. Estimate the cost of reinstating gauges or incorporating local gauges to satisfy WSC specifications (minimal standards are noted below the sheet's legend). If the gauge is in operation, please identify the current funding source. Where possible, please specify the location using UTM or Lat./Long. coordinates; otherwise please describe the general location by referencing the position on the stream with respect to tributaries, built-up areas, etc. The table also inquires if your agency has a digital watershed boundary available for each specific gauge site. Note that within the Excel workbook, we have included a Decommissioned Gauges worksheet that may contain helpul information when filling in the table (i.e. reinstated sites). After validating the spreadsheet information and adding the information for the gauges above, please save the spreadsheet and forward to ahouse@trentu.ca as an attachment - Thanks.

Carefully check the information you have entered before submitting.

Watershed Science Centre
Trent University, Symons Campus
1600 West Bank Drive
Peterborough, Ontario, K9J 7B8
Phone: 705-755-2211, Fax: 705-755-2276

http://www.trentu.ca/wsc/