Donald, based on the data, it is correct. You just divide "current" stats on acre-feet of water by surface area, then compare this to full lake stats. I did it and it checks out.

Hmm? I know you are a stickler for mapping accuracy to optimize angling opportunities and I thought I'd share some math that relates to your low Choke Canyon Lake. Some stuff below. It shows that as a foot of additional water level is added to Choke Canyon, it raises the average depth of the lake by a fraction of the full foot, usually falling in the 30 to 50% range. The reason, and this relates to your contour lines, is as a lake adds each foot of water, it increases its area. Again, the attached chart shows that, generally, for each foot of water column added, about 500 acres of additional lake coverage occur. This additional acreage will be concentric . . . increasing its, what, "belt size" around its shoreline. This is what causes the average depth of a lake to drag behind a full foot of column water increase (or decrease). Our lakes have slope. To be 1:1, it'd take vertical walls as shorelines, then your contour lines' depths would change 1:1 with increasing or decreasing water levels.

Anyway, sum up the acres in the far column from 220' to 196' and that is how much acreage has shrunk . . . taking some of your contour lines along for the ride.

Brad


Ft Surface Acres Acre-ft Avg. Depth Gain % Added acreage
195 12,076.00 189,763.22 15.71407917
196 12,567.00 202,085.89 16.08067876 36.66% 491.00
197 13,035.00 214,889.92 16.48560951 40.49% 468.00
198 13,512.00 228,163.52 16.88599171 40.04% 477.00
199 14,005.00 241,915.50 17.27350946 38.75% 493.00
200 14,676.00 256,258.58 17.46106432 18.76% 671.00
201 15,232.00 271,221.97 17.80606421 34.50% 556.00
202 15,737.00 286,712.91 18.21903222 41.30% 505.00
203 16,144.00 302,657.15 18.74734576 52.83% 407.00
204 16,539.00 318,997.48 19.28759175 54.02% 395.00
205 16,954.00 335,741.41 19.80307951 51.55% 415.00
206 17,409.00 352,919.50 20.27224424 46.92% 455.00
207 17,919.00 370,577.35 20.68069368 40.84% 510.00
208 18,453.00 388,763.39 21.0677608 38.71% 534.00
209 18,988.00 407,484.21 21.46009111 39.23% 535.00
210 19,523.00 426,739.82 21.85831173 39.82% 535.00
211 20,058.00 446,530.22 22.26195134 40.36% 535.00
212 20,593.00 466,855.41 22.67058758 40.86% 535.00
213 21,242.00 487,750.03 22.96158695 29.10% 649.00
214 21,722.00 509,245.31 23.44375794 48.22% 480.00
215 22,244.00 531,219.37 23.88146781 43.77% 522.00
216 22,853.00 553,757.42 24.23127904 34.98% 609.00
217 23,558.00 576,956.01 24.49087401 25.96% 705.00
218 24,145.00 600,818.10 24.88374819 39.29% 587.00
219 24,689.00 625,233.93 25.32439264 44.06% 544.00
220 25,173.00 650,178.52 25.82840822 50.40% 484.00