INSIGHTS:

LAKESHORE CAPACITY MODEL , Updating the Current Approach

This article appeared in the "Keeping Your Lake Great" FOCA May 2000 newsletter. Prepared by Randy P. French, Chairman, Land Use Committee.

Background
Since the mid 1970's the Ministry of the Environment (MOE) have used a water quality assessment model to set development capacities on lakes throughout Ontario. The model, called the Lakeshore Capacity Assessment, is based on predicting the inputs of one key pollutant, that being anthropogenic (man made) sources of phosphorus from septic systems. The Lakeshore Capacity Model is a planning tool that will help to achieve a consistent approach to protecting water quality by defining shoreline development capacities on inland lakes across the province.

The primary purpose of the model is to predict how much residential and commercial development a lake can sustain without impairing its water quality. For many years, the MOE and the Ministry of Natural Resources (MNR), in conjunction with local municipalities, have used this model to protect recreational water quality and lake trout habitat on many lakes throughout Ontario.

The model, first developed in 1975, quantifies linkages between natural sources of phosphorus to a lake, human impacts from shoreline development, water balance, the size and shape of a lake, and the resultant phosphorus concentrations. The model uses a number of assumptions about phosphorus loadings, phosphorus retention, and useage figures. The model allows the user to calculate how water quality in a lake will respond to the addition or removal of shoreline development such as cottages, permanent homes and resorts. It predicts several important indicators of water quality: total phosphorus concentration, algal density (chlorophyll a concentrations), water clarity (Secchi depth), oxygen concentrations in the bottom waters at the critical end of summer period and the volume of lake trout habitat.

The Ministry of Natural Resources use the model to predict the impact that development will have on Lake Trout Habitat in cold water lakes. Lake Trout have two basic habitat requirements, temperature and dissolved oxygen. When phosphorus is added to a lake, it creates algae, and when algae settles at the bottom of a lake it decomposes and uses up available dissolved oxygen. Through research, the MNR have determined that the recommended minimum dissolved oxygen criterion for the protection of lake trout populations is 7 mg L-1. Lake Trout lakes that are below the 7 mg L-1 criterion would have no further capacity for phosphorus loading and lakes that exceed the criterion would have some capacity.

The New Handbook
A few years ago, MOE initiated a review of the Lakeshore Capacity Assessment model with the Ministry of Natural Resources (MNR) and the Ministry of Municipal Affairs (MMA). These three ministries intend to release a Handbook to provide guidance to municipalities and other stakeholders, such as lake associations, on the use of the model in order to promote consistent application across the province.

The handbook is intended as a guide and a resource for municipalities and is not a compliance document. Although there is no requirement for municipalities to conduct the lakeshore capacity assessment, MOE recommends its use to help plan development of inland lakes in a manner that protects water quality. The handbook also provides a number of Best Management Practices to minimize the migration of phosphorus to water bodies, thus reducing the impacts of development on water quality. Some of these include: increasing the setback of septic systems from shorelines, maintaining and installing vegetative buffers, as well as designs and practices for septic systems.

FOCA's Involvement FOCA is very interested in the application of this model as it helps local lake associations to control the total number of residential lots and commercial units that a lake can sustain. With the help of Gerry Hunnius, Margaret Casey and Randy French, FOCA has been involved in the review of the Handbook and completion is expected later this year. Training sessions on the model will be provided and we are hope to arrange a special course for our Lake Stewards. FOCA members have attended several meetings and have recently provided comments on the third version of the Handbook.

FOCA recognizes that there are many lakes throughout Ontario that would benefit from the application of the model and urges the three ministries to complete the handbook as soon as possible.

FOCA's Concerns
While the Lakeshore Capacity Assessment model will encourage land use decisions that will maintain and enhance water quality of our lakes we remain concerned that it only addresses the setting of lake wide development capacities based on one component - phosphorus loadings from septic systems. Other factors that help define development capacities of our lakes are not included, such as; natural elements (specific wildlife and fish habitat, and vegetation); the physical capability of the shorelines (topography, soils, existing development, landscapes, narrow waterbodies, steep slopes); and social elements (aesthetics, cultural/historic values, boating limits and crowding). Although this is a realistic concern, we recognize the urgency with completing the Handbook because it will help to protect one of our keystone interests, water quality.

Another matter that FOCA is concerned about is the introduction of new phosphorus abatement technology. The Handbook recommends that the use of "approved" phosphorus abatement technologies should only be considered for lakes that have significant development capacity remaining. "Experimental" systems will only be considered where existing conventional sewage has failed and should not be tested on lakes that are at or near capacity. FOCA agrees with this approach.

This is a valuable handbook for our lake stewards and others. We will continue to work with the three ministries in an effort to have the final product available as soon as possible.