Current Monitoring

Secchi Disk Sampling
The disk is named after Pietro Secchi, a Jesuit scientist, who studied the Mediterranean Sea in the mid-1800's. The Secchi disc is a simple scientific instrument used to measure water transparency. The Secchi disk is an eight-inch disk painted with alternating black and white quadrants. The disk is lowered into the water until it can no longer be seen by the volunteer. This depth of disappearance is a measure of the water's transparency. The Secchi disc depth indicates the water transparency and provides a rough estimate of light penetration in the water column. As a general rule, light can penetrate to a depth of two times the Secchi depth. If the Secchi depth was ten feet, then light can penetrate to a depth of 20 feet (10 feet x 2 = 20 feet). As light penetration increases, so does the amount of plant growth and oxygen produced by algae and aquatic plants.

The Citizen Lake Improvement Program (CLIP) was established in 1990 with the goal of monitoring area lakes, ponds and reservoirs. The Indian Lake Secchi disk sampling is done by CLIP volunteers. CLIP is sponsored statewide by the Ohio Lake Management Society and locally by the Indian Lake Watershed Project. The monitoring is performed by trained local volunteers. Lake users and watershed landowners can use water quality monitoring data to evaluate the effects of changes in land management and understand the lake ecology.

Ohio CLIP volunteers have collected data on over 60 Ohio lakes, ponds and reservoirs. Indian Lake volunteers started sampling in 1989, before CLIP was established and have provided more data to CLIP than any lake in the program. Indian Lake not only has the oldest CLIP/Secchi disk program, it has the largest number and most active group of volunteers on a single CLIP program in Ohio. These volunteers sample their designated locations twice a month from May to October. The data collected includes: water transparency using the Secchi disk, water color, water and air temperature, water depth, wind, rainfall, cloud cover, lake level and recreational use.

Average Secchi Disk Readings For Indian Lake

Parameters	1989	1990	1991	1992	1993	1994	1995	1996
Number of Volunteers	9	3	13	11	11	12	12	15
Number of Readings Taken	33	16	115	113	104	125	95	No Data Yet This Season
Ave. Secchi Depth Reading in Inches	12.7	12.4	11.4	13.2	15.7	13.4	14.3	No Data Yet This Season

Average Monthly Secchi Disk Readings For Indian Lake*

Month	1989	1990	1991	1992	1993	1994	1995	Average Per Month
May	**	13.5	14.2	17.1	26.2	18.3	17.3	17.8
June	**	11.8	12.3	12.9	18.5	13.5	17.8	14.5
July	**	**	10.2	11.5	14.2	11.9	12.9	12.1
August	11.0	11.5	10.3	11.2	10.2	11.1	12.2	11.1
September	13.4	12.7	9.9	11.7	11.6	12.2	12.5	12.0
October	13.6	**	11.5	14.9	13.6	13.3	13.3	13.3

*Recorded in Inches
** No Data Recorded

Results
In comparing the Indian Lake data from 1991 to 1995, there were slight changes in the average Secchi depth and color in Indian Lake. More conclusive analysis needs to be conducted on this data before drawing any concrete answers. There are many variables which need to be considered. The average monthly Secchi Disk readings show favorable trends. Interesting trends in the data are seen in the May and June readings. These two months reveal a gradual increase in readings which means there is greater transparency in the lake at these times of the year. Secchi Disk readings can be affected by many variables like rain fall, sunshine, wind, boat traffic, following proper sampling procedures and many others.

It is speculated that the higher readings in May and June are due in part to the lower amount of boat traffic which stirs sediment from the bottom. The reduction of soil loss (tons/acre/year) in the watershed has increased every year and the early secchi disk readings (May and June) have increased since the start of the watershed project. A more comprehensive study is needed to determine if a correlation between increasing water transparency readings and watershed soil erosion reduction practices exists.

The change in color samples suggests Indian Lake transparency was most affected by sediment in 1991 and more affected by algae since. Obtaining chlorophyll samples for the lake would assist in determining the amount and extent of algae growth in the lake. The chlorophyll data would also give insight on whether the low transparency readings are more from suspended sediment or from algae. Samples are affected by many variables, yet give a relatively creditable picture of the lake transparency. The sediment issues seem to be improving. As the sedimentation becomes less of a problem, the increase in algae becomes more of a concern in regards to water quality, water transparency, and a host of concerns not associated with sedimentation issues. It appears clarity has improved since 1991, but additional data is needed to verify this trend, especially since climatic conditions varied during the same time period. This is why it is important that water quality monitoring continue on Indian Lake. Volunteer and professionally collected data will provide the documentation to show the beneficial results of soil conservation and lake management practices.

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