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SWEEP Report #76

Executive Summary
(PWS Report #8)

R. R. Walker, Beak Consultants Ltd, Guelph, Ont., and J. Sadler Richards, Ecologistics Ltd., Waterloo, Ont.

Executive Summary

Evaluation Summary (Tech. Transfer Report Summaries)

View / Download Final Report  [206 KB PDF]

Associated SWEEP/LSP Research



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Completed: September, 1994

Note: This report consists of the executive summaries for the other seven Pilot Watershed Study reports. The Introduction is presented here, as well as the Evaluation Summary from SWEEP Report #79.

This report is referred to as "Report #77" in SWEEP Report #79. Several copies of this report were also stamped "Report.107".

Key Words:

agricultural watersheds, water quality, erosion, phosphorus, conservation tillage, watershed modelling, soil quality, hydrology, residue management, rainfall simulation, cooperator attitudes, program implementation




The Soil and Water Environmental Enhancement Program (SWEEP) was initiated in 1986 with an overall mandate to:

  • reduce Ontario's Non-Point Source (NPS) loadings of phosphorus to Lake Erie from agricultural sources by 200 tonnes; and

  • maintain or improve the productivity of the primary agricultural sector in Southwestern Ontario by reducing or correcting soil erosion and degradation.

The Pilot Watershed Study (PWS) is a major SWEEP sub-program aimed at evaluating and demonstrating the benefits of established conservation farming systems at the watershed and smaller scales. Figure 1.1 shows the overall SWEEP organizational structure and the PWS sub-program relationship to the Program. Cooperating agencies; Environment Canada (EC), Agriculture Canada (AC), and the Ontario Ministry of the Environment (MOE) are identified. Beak Consultants Limited (BEAK) is the prime contractor responsible to AC and MOE. Ecologistics Limited (ECOLOGISTICS) is a sub-contractor to BEAK responsible for site selection and the agronomic program of the PWS.

The PWS started in 1987 with detailed study design, staffing, training, cooperator enlistment, and watershed selection. Farm plans were initiated in August, 1988 and environmental monitoring began later the same year.

Monitoring and evaluation were conducted from late 1988 until mid 1992.

Figure 1.2 shows the location of PWS subject areas within the Lake Erie Watershed. These are situated within different yet common agricultural and physical settings.

The PWS has the following key features:

  • four year implementation and monitoring period;

  • test (conservation oriented systems) and control (conventional systems) paired watershed design;

  • pro-active agronomic management involving annual farm planning, cooperator compensation program, ongoing producer extension program, availability of conservation-type farm implements, detailed cooperator record keeping, crop scouting and productivity analysis, and farm level socio-economic evaluation;

  • intensive and continuous environmental monitoring at plot, field and watershed scales;

  • detailed soil survey and soil quality monitoring;

  • extensive environmental monitoring program including meteorology, hydrology and water quality; and

  • detailed evaluation involving the application of two modelling systems for farm planning and systems evaluation.

The paired watershed study design is a unique approach which relies upon direct comparisons between the test and control areas as the primary method of environmental and agronomic evaluation. The effects of scale, at whole watershed, farm, field and plot scales are also a fundamental aspect of the study design which systematically addresses the relationship between producer attitudes and adoption as well as between measurable benefits, complexity, and scale.


Objectives of the Pilot Watershed Study

Objective Regarding Study/Approach

To achieve a high level of adoption of the most appropriate soil and water conservation practices among farm operators utilizing lands in the test sub-watersheds.

Objective Regarding Effectiveness

To determine the nature and degree of changes in relevant soil and water quality parameters and crop yields as influenced by "basin-wide" soil and water conservation practices.

Objective Regarding Information Dissemination

To prepare information about sub-program activities and results and to transmit this to participating farmers and other related SWEEP sub-programs.

Report Structure

The overall PWS reporting has been sub-divided into the following categories:

  • Report #1, Study Area Selection, Description and Climate (SWEEP Report #69)

  • Report #2, Implementation of Conservation Systems (SWEEP Report #70)

  • Report #3, Evaluation of Conservation Systems, Social Factors (SWEEP Report #71)

  • Report #4, Evaluation of Conservation Systems, Soils and Crops (SWEEP Report #72)

  • Report #5, Evaluation of Conservation Systems, Hydrology (SWEEP Report #73)

  • Report #6, Evaluation of Conservation Systems, Water Quality (SWEEP Report #74)

  • Report #7, Modelling (SWEEP Report #75)

  • Report #8, Executive Summary (SWEEP Report #76)

Each report is a stand alone document including a summary, descriptions of objectives, methodologies, observations, discussion, and summarized listings of relevant data where applicable. The Executive Summary is a compilation of summaries with emphasis on conclusions and recommendations extracted from the seven technical reports.


Evaluation Summary

(From Technology Transfer Report Summaries - A. Hayes, L. Cruickshank, Co-Chairs)

The Pilot Watershed Study (PWS) was designed to evaluate the environmental benefits as well as the agronomic and socio-economic implications of conservation farming systems when applied over whole agricultural watersheds. The study design and evaluation program was based upon the use of paired test and control watersheds. The control watershed cooperators were encouraged to continue with conventional farming practices while the test watershed cooperators were encouraged to adopt conservation farming systems during the course of the study.

Over 75 cooperating farms were involved in the study over a four year period. Three pairs of watersheds (test vs. control) were selected to be representative of three different, yet common farming environments in terms of crop rotations, soils and topography within the Lake Erie Watershed. The study areas were selected at the earliest stage of the PWS and are located in Essex County, (east of the town of Essex) an area representing primarily cash cropping with row crops/grain rotations on flat poorly drained clay soils; in the headwaters of Kettle Creek, (north of St. Thomas) representing rolling landscapes with mixed farming involving row crops/grain rotations and swine production on silty loam soils; and in the headwaters of the Gordon Pittock Reservoir (north of Woodstock) where row crop/grain rotations are maintained along with swine and dairy operations on an undulating landscape.

Implementation of Conservation Systems

As a proactive and targeted program the PWS identified specific geographic areas where soil degradation/water quality problems were of interest and where adoption of soil conservation measures by local cooperators would have the greatest impact on soil erosion control and sediment delivery to water courses. Within the PWS an incentive package was required to promote change (i.e. the adoption of conservation practices) and general cooperation within the time frame of the study so that objectives could be realized. The incentives were formulated on the basis of access to information, experience, specialized equipment and financial grants. Cooperators signed agreements with the PWS that outlined the responsibilities of each party. The agreements were amended annually and included changes to conservation farm plans by test cooperators or confirmed the maintenance of records by control watershed cooperators. During the project approximately 89% of eligible landowners/managers participated in the program (e.g. 65 out of a possible 73 in the final year).

To meet the objectives of the PWS conservation farm plans were developed with the test cooperators which identified the management techniques that would be used to maintain soil productivity and improve water quality in the associated test watersheds. The approach involved the integration of watershed computer modelling used to predict the impacts of current watershed management practices with farm and field level conservation planning. This integration effectively made the watershed modelling tool into a planning tool that could be used to estimate the potential combined effects of individual farm plans on the watershed before any work was done on the ground. With this information a unique opportunity to adjust plans in order to meet watershed soil erosion and sediment delivery targets was available. A two level approach was used that involved first, a background analysis step and second, a field discussion step.

Indicators of Adoption and Cooperator Attitude Changes

The incidence of conservation practices in the test watersheds increased positively during the study. The study time frame represented the early adoption phase which is often characterized by a relatively steep participant learning curve. Within the first three years of the study approximately 81% of identified conservation crop and tillage actions and 52% of conservation structures were completed by the test cooperators. The shift in acreage that was moldboard ploughed versus no tilled was also dramatic.

Documented changes in cooperator attitudes toward soil and water conservation resulted in several conclusions including the following:

  1. Implementation of erosion control measures resulted in test cooperators perceiving less erosion occurring on their farms in 1992 relative to 1988. Conversely, control cooperators saw the same amount or slightly more erosion happening on their farms over the same time period. Control cooperators likely became sensitized to erosion problems as a result of the PWS, but did not receive encouragement to implement measures within the watershed boundaries to alleviate the problem.

  2. Test cooperators were generally neutral or slightly positive about practice effects on crop yields. They were almost always more positive with respect to effects on profitability. This bodes well for future adoption as cooperators appeared to be acknowledging the net financial benefits of implementation of even the less familiar practices.

  3. In general, cooperators agreed that five to ten years was a realistic time frame for achieving a satisfactory comfort level with conservation planting equipment. This took into consideration extremes in weather, shifting weed populations, fine-tuning equipment to variable soil textures and moisture conditions, and the application of conservation planting to all crops in the rotation. Some suggested a three-year time frame may be adequate for developing confidence in no-till wheat production.

  4. When asked about their post PWS conservation intentions, a strong majority of farmers in both the test and control watersheds intended to increase or maintain the same acreage under conservation practices. The primary exception to this was the adjusted or modified moldboard plow which many said they would either discontinue or didn't know whether they would continue. Seventy-four percent of the test cooperators and 38% of control cooperators said they would maintain or increase their acreage under no-till.


Watersheds were fully instrumented and monitored from late 1988 until June 1992. Residue management in the test watershed resulted in generally higher cover levels in test watersheds over the course of the study. In the latter stages of the study, test watershed cover exceeded control watershed cover by an average of 17%.


During the study monitoring period (1989-1992) the precipitation deviated significantly from normal trends. While above average or average precipitation was desired in order to rigorously test the conservation systems implemented, well below normal precipitation was experienced in 1989, 1991 and the first six months of 1992. Winter precipitation and snowfall were well below normal resulting in minimal snow cover and modest spring melt events. Severe storms were rare during the study period. Precipitation was near normal in 1990 on the whole and exceeded the normal precipitation during the later summer months.

Test and control watershed pairs experienced very similar weather throughout the study although total event precipitation did differ significantly on occasion.


Streamflow was measured continuously by the Water Survey of Canada at the watershed mouths. Surface run-off was monitored at field scale monitoring sites from most of the significant precipitation events. Total run-off generated from 1 metre square plots during simulation storms was measured and recorded. Watershed scale, field scale and plot scale run-off behaviour was examined and compared between corresponding test and control sites. Run-off was also related to conservation system effects using cover (live and dead) as the primary independent variable to determine whether run-off increases or decreases under conservation tillage.

In Essex, watershed and field scale run-off increased under conservation systems while plot scale studies indicated a general reduction in run-off. In Kettle Creek, watershed scale evaluations indicated a reduction in run-off with increased cover while plot scale evaluations indicated the reverse. The field scale evaluations in Kettle Creek were inconclusive.

In Pittock, the watershed scale and field scale studies were inconclusive, partly due to a lack of data. Pittock was generally drier, producing fewer significant run-off events. Plot scale studies in Pittock indicated a positive relationship between cover and run-off.

Plot scale studies in Essex also indicated that, in general for pre-plant periods, total run-off was highest from control plots with less plant residue and run-off from the control plots exceeded run-off from other times. In Kettle Creek test plot run-off generally exceeded control plot run-off during pre-plant and post tillage periods when test plot residues were highest. No differences were observed for post harvest times when cover was similar in both set of plots.

In Pittock, test run-off exceeded control run-off during post tillage periods when residues differed significantly.

Pre-plant period run-off was generally highest for all areas combined. Post tillage run-off from control plots was generally the lowest due to high surface detention storage and surface roughness.

Overall, test plot run-off exceeded control plot run-off in this aspect of the study.

Water Quality Loadings

A continuous record of water quality loadings was generated for each watershed, for events at the field scale, and for each rainfall simulation measurement.

In Essex, the watershed scale total suspended solids (TSS) and total phosphorus (TP) data indicated that a trend to improvement in the test watershed may have started in 1991 and continued through the first half of 1992. However, this observation was not statistically significant as test and control unit area loadings have been very similar throughout the study. At the field scale a definite inverse relationship between cover (live and dead) and TSS and TP loadings has been identified. The relationship shows that as event run-off increases the improvement in run-off water quality in the test watershed over the control increased. That is, the benefit afforded by cover becomes most evident during more extreme precipitation events. At the plot scale, control plot run-off of TSS and TP is significantly higher than the test plot run-off in the pre-plant and post tillage periods.

Run-off loadings during the post harvest period, when cover levels are similar, is not significantly different between test and control plots. Rainfall simulation measurements also indicated that run-off loadings are highest during the pre-plant period for both test and control plots.

In Kettle Creek, at the watershed scale, a similar trend, as observed in Essex, may be in effect. The 1991 and 1992 test watershed loadings tended to decrease relative to the control loadings especially for TSS. While these results are not statistically significant, the trend is positive. The field scale studies show a marked improvement in run-off loadings for TSS and TP from test fields when compared to control fields at high run-off flow rates. In Kettle Creek, the positive benefit is shown to occur only for high flow events.

The plot scale studies for Kettle Creek are similar to those for Essex. Control run-off loadings for TSS and TP are significantly higher than test plots during the post harvest and pre-plant periods. Post tillage run-off loadings are low and not significantly different. While improvements in test run-off loadings are significant they are not as pronounced as in Essex. Pre-plant and post-tillage periods generated the most run-off loadings of TSS and TP in both test and control plots.

At the watershed scale, Pittock test loadings of TSS and TP were lower than control in 1990 when the test watershed achieved the highest cover values, exceeding overall cover in the control watersheds. Test watershed cover decreased in 1991 and 1992 reflecting a lower level of cooperator enthusiasm in Pittock. A comparison of watershed loadings between test and control after 1990 was not statistically significant. The Pittock area received less precipitation and much fewer field scale surface run-off events. Only one of four microbasins had sufficient data to evaluate the effect of cover on run-off loadings of TSS and TP. That field scale site indicated that TSS and TP loadings were inversely related to cover, as hoped. At the plot scale the overall loadings of TSS and TP were highest from the control plots. This was due to high control plot loadings during the pre-plant period. Run-off loadings of TSS and TP for the post-harvest and post tillage periods were significantly higher from test plots although overall loads were low during these periods.

Generally, cover was shown to reduce run-off loadings of TSS and TP from watersheds, fields and plots. Results at the plot and field scale are statistically significant. At the watershed scale, general improvements in test watersheds over control watersheds may be in effect over the last 12 to 18 months of the study. These trends are not statistically significant. These observed trends coincide with the management of higher crop residue levels in test watersheds. These results are highly positive in light of the fact that these evaluations have been conducted for a transition period and more dramatic improvements in test watershed loadings relative to control watersheds is likely as soil quality and farmer confidence and familiarity are improved.


It is unfortunate that this study was conducted over a relatively short period of time. Some trends were beginning to emerge but the limited amount of data made it difficult to draw any definite conclusions regarding effectiveness at the watershed scale. Smaller scale research areas identified positive environmental benefits. Ideally the study could have monitored the watersheds for three years while conservation tillage was being implemented and then for three to five years after implementation. In this study the entire monitoring period was an adoption-transition phase in terms of soil structure and social factors such as farmer education and farm management. The study did not run long enough to allow for collection of data from the watersheds during a post-transition period.

The two years of abnormal weather (generally low precipitation amounts for the period) made it difficult to build a large base of information for use in evaluation of the conservation tillage system. The watersheds generally did not experience extreme precipitation events which are necessary to test the systems in place.

Associated SWEEP/LSP Research:

  • SWEEP Report #69 - Pilot Watershed Study Report #1: Study Area Selection, Description and Climate

  • SWEEP Report #70 - Implementation of Conservation Systems (PWS Report #2)

  • SWEEP Report #71 - Evaluation of Conservation Systems: Cooperator Attitude Change (PWS Report #3)

  • SWEEP Report #72 - Evaluation of Conservation Systems: Soils and Crops (PWS Report #4)

  • SWEEP Report #73 - Evaluation of Conservation Systems, Hydrology (PWS Report #5)

  • SWEEP Report #74 - Evaluation of Conservation Systems, Water Quality (PWS Report #6)

  • SWEEP Report #75 - Watershed Modelling (PWS Report #7)

  • SWEEP Report #62 - Volume I - An Economic Evaluation of Soil Conservation Technologies, Summary Report

  • SWEEP Report #63 - Volume II - Collection and Analysis of Field Data in the Pilot Watersheds Study

  • SWEEP Report #64 - Volume III - Field Level Economic Analysis of Changing Tillage Practices in Southwestern Ontario

  • SWEEP Report #67 - Volume VI - Watershed Level Economic Analysis of Tillage Practices in Southwestern Ontario

Future Research: ( ) indicates reviewers suggestion for priority, A - high, C - low.

(A) The watershed studies should be continued for three to five more years to evaluate the test following the adoption period. This is consistent with the time frames for agricultural watershed scale studies conducted elsewhere in North America.




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Created: 05-28-1996
Last Revised: Thursday, May 19, 2011 07:53:10 PM