Proceedings of the Iowa Academy of Science Volume 80 Number Article 4 1973 Some Relationships Between Morphometry and Thermal Stratification in Some Iowa Lake Basins James Mayhew Chariton Research Station, Red Haw State Park Let us know how access to this document benefits ouy Copyright ©1973 Iowa Academy of Science, Inc. Follow this and additional works at: https://scholarworks.uni.edu/pias Recommended Citation Mayhew, James (1973) "Some Relationships Between Morphometry and Thermal Stratification in Some Iowa Lake Basins," Proceedings of the Iowa Academy of Science, 80(4), 162-166. Available at: https://scholarworks.uni.edu/pias/vol80/iss4/4 This Research is brought to you for free and open access by the Iowa Academy of Science at UNI ScholarWorks. It has been accepted for inclusion in Proceedings of the Iowa Academy of Science by an authorized editor of UNI ScholarWorks. For more information, please contact [email protected]. Mayhew: Some Relationships Between Morphometry and Thermal Stratification Some Relationships Between Morphometry and Thermal Stratification in Some Iowa Lake Basins JAMES MAYHEW 1 MAYHEW, JAMES. (Chariton Research Station, Red. Ha~ State area development and volume development. Strongly stratified Park, Route 1, Chariton, Iowa 50049.) Some Relationships Be­ lakes had the greatest maximum and mean depth, basin slope, area tween Morphometry and Thermal Stratification in Some Iowa development and volume development. Lakes with unstable and Lake Basins. Proc. Iowa Acad. Sci. 80( 4): 162-166, 1973. temporary stratification had lower values for basin configuration. SYNOPSIS: Thermal stratification of five man-made lakes in southern Unstratified lakes had the lowest morphometric indices. The use Iowa are studied in relation to basin morphometry. The lakes of these indices for predicting the tendency for stratification of a were Red Haw Lake, Lacey-Keosauqua Lake, Green Valley Lake, basin prior to dam construction was discussed. Lake Keomah and Lake Darling. Form of the water mass was INDEX DESCRIPTORS: Thermal stratification, basin morphometry, compared by three mathematical indices including basin slope, mathematical indices. Thermal stratification occurs quite commonly in man-made during three years. Atmospheric temperatures during the per­ lakes of the midwest region and is prevalent in small Iowa iod of stratification varied insignificantly each year, and high­ impoundments with a maximum depth of 24 ft or more. er temperatures appeared most important during initial for­ Closely associated with typica~ stratified temp~rat~ l~es of mation of thermal stratification. The intensity and stability order two, according to Welsh s ( 1935) classificat10n, is de­ of stratification along with the thickness and location of the pletion of dissolved oxygen within ~he h~olimnion .. Where metalimnion were functions of basin characteristics and form the water surface is sheltered from wmd action, low dissolved of the water mass. oxygen concentrations often extend upwards into the meta­ limnion. Investigations by Dendy ( 1945), Sprugel ( 1951) ~nd METHODS AND PROCEDURES Byrd (1951) showed thermal stratification was the principal Five man-made lakes from widely separated locations in factor associated with limited vertical distribution and move­ southern Iowa and greatly different in size, depth, topography ment of fishes. Studies at Red Haw Lake, Iowa, by Mayhew and intensity of thermal stratification were selected for com­ ( 1963) revealed stratification had profound influence on parison. Red Haw Lake and Lacey-Keosaqua Lake were ther­ both the vertical distribution and seasonal growth of several mally stratified and had oxygenless hypolimnions. Green Val­ fish species. Seasonal influence of stratification was so com­ ley Lake and Lake Keomah stratified temporarily during plete in summer months it formed the substru.cture. upon windless periods with high atmospheric temperatures, and which the whole biological framework rested. Fish b10mass occasionally had low dissolved oxygen levels near the bot­ was reduced by stratification from crowding of fish into the tom. Lake Darling never stratified and contained high dis­ shallow, oxygenated level and reducing the amount of avail­ solved oxygen concentrations at all depths. All of the lakes able habitat. Failure of many fishermen to recognize the lake were state-owned recreation impoundments located in state was stratified and devoid of dissolved oxygen below 12 ft parks and were mapped prior to dam construction. Tempera­ was responsible for a large number of unsuccessful fishing ture and dissolved oxygen profiles were taken at least twice during the summer months for seven consecutive years. ( 1956) found wide variation in the intensity of tri1M~en Thermal stratification and lake basin morphometry were thermal stratification at man-made lakes in southern Iowa, compared through a series of mathematical indices for basin and classified the impoundments into three different groups. slope, area development and volume development. The in­ The first group was most characteristic of temperate lakes of dices defined the physical characteristics of the basin as a order three, nearly homothermous from surface to bottom cone whose height and basal area were identical with the with high dissolved oxygen concentrations at all depths. The form of the water mass. Area and volume development for second group stratified temporarily in summer months and individual lake basins were graphically illustrated and slope seldom had a well defined hypolimnion, although dissolved was computed for each 5-ft contour and for the mean of all oxygen concentrations often reached low levels near the lake contours. Individual lake basins were compared on the uni­ bottom. The third group exhibited the classical temperature­ formity or diversity between one or more of these parame­ dissolved oxygen profiles for temperate lakes of order two, ters. having three well defined strata and complete loss of dis­ Slope of basin walls described the water mass in two di­ solved oxygen in the hypolimnion. mensions using the length of each contour and the vertical The Red Haw Lake studies by Mayhew ( 1963) showed distance between contours. Slope of basin walls containing slight change in the location of the metalimnion each summer each isobath was computed for the generalized function 1 Supervisor of Fish Research, Chariton Research Station, Red Slope = ~CI : C ~ ~ Haw State Park, Route I, Chariton, Iowa 50049. Published by UNI ScholarWorks, 1973 1 Proceedings of the Iowa Academy of Science, Vol. 80 [1973], No. 4, Art. 4 LAKE MoRPHo:-.rnTHY AND STRATIFICATION 163 where ceeded 15° F. cl and c~ = length in ft of the two contours Basin indices showed high values for all parameters, char­ V = vertical distance or interval in ft between acteristic of a lake basin with steeply sloped walls, small area contours of shallow depth and systematically increased association be­ A = surface area of the lake in acres multiplieJ tween basin development and depth. Slope of contours by .004536. ranged from 3.6% to 18.6% but averaged 8.6%. The hypso­ Mean slope for the basin was mathematicallv derived from graphic curve (Figure 1) showed an inverse association be- the equation l/2C +C +C + X slope= 0 I 2 0 o-_ N ... .... where 5 0 .... ... • .... C 11 , C 1 , C 11 = length in ft of each contour ... N = number of contours ' ' ' D = maximum depth of the lake in ft 10 • 0 ' ... A = surface area of the lake in acres multiplied by .004356. ' \ Change in basin shape was reflected in both the singular 15 o' and mean slope associations and was expressed in percent >- • \ LL values. As walls of the basin became steeper there were pro­ '!': \ portional increased values for both slope between contours I >- 20 'o, and the mean slope of the whole basin. Q_ ' UJ \ Area development was determined for each impoundment 0 \ by plotting a percentile hypsographic curve which represented \ a three dimensional profile of all elements characteristic of 25 • \ ,o \ the basin form. As area development increased there was an \ \ inverse association between the variables, and the slope of the \ \ curve was systematically steeper. The reverse occurred with 30 0 lesser area development. • Volume development was expressed by plotting the .;l-acre 100 90 80 70 60 50 40 30 20 10 ft values between the total basin volume and the volume for •1. SURFACE AREA each successive contour. The form of the water mass was further defined by an index value from the generalized equa­ 10 9 8 6 5 4 tion 6- VOLUME IN ACRE FT X102 3 ·o Volume development= mean Figure 1. Area and volume development of the Red Haw Lake D max basin. Dashed line is percent hypsographic curve and solid line is .;l-volume curve. Both lines were fitted by eye. where Dmenn is mean depth and Dmax is the maximum depth. This expression represented the ratio of total volume to an infinite cone whose volume development was identical with tween area and depth. At 10 ft more than one-half of the the lake basin. When the value was equal to unity the form total area at spillway elevation remained and more than 25% of the basin was a perfect cone; when the basin walls were of the total area remained at the 20-ft contour. Volume de­ convex toward the surface, the index was less than unity; and velopment for the basin was 1.08, indicating the basin walls when basin walls were concave toward the surface, the index were slightly concave toward the water surface. value was greater than unity. Lacey-Keosauqua Lake This lake is located in Lacey-Keosauqua State Park near Keosauqua in Van Buren County. Maximum surface area at RESULTS spillway crest elevation is nearly 35 acres. The lake has a Red Haw Lake maximum depth of 26 ft and a mean depth of 16 ft. The dam The lake is located in Red Haw State Park near Chariton is located in a very deep, heavily wooded valley which af­ in Lucas County. At spillway crest elevation the lake con­ fords nearly total protection to the water surface at all times.