Typically, how many inchess of rain results in a foot of lake level increase?
I know it varies from lake to lake, but what's a guesstimate? Our lakes in DFW are getting crazy low. I'm running out of ramps to use in some of my favorite lakes....and I'm running out of shallow cover to flip to! Haha.

I researched this exact same topic several years ago when the lakes were REALLY low and there isn't a direct answer to any of it. There are way too many factors involved such as: number of major or minor feeder creeks, ground moisture level prior to the rain, temperature, rain rate (how fast it fell), etc.

I can tell you this, when we got heavy rains on cold wet grounds, the result I saw on Cypress Springs a few years ago was 7" of rain became 2.5' of water. That rain followed a snow event in the area.

https://water.usgs.gov/edu/earthrain.html

https://waterdatafortexas.org/reservoirs/statewide

What you could do is pick your reservoir and then look at historical levels before and after a specific rain event. That might give you an idea.

It also varies on time of year and how long it's been since the last rain.

Example: August, hasn't rained in 2 months. It rains a good amount 2-3 inches in 12 hours. Just about all the rain will be soaked up by the ground before it reaches the watershed.


The rain we are getting today: It rained for a few hours on Saturday--it was a good rain, especially Dallas and south. Before Saturday, we hadn't had a good rain since October. Most of it probably went to the ground before it reached the watershed. Now that the ground is saturated, today's good rain (and hopefully again on Friday) will reach the lakes.


Searching the Internet, there's been some recent studies on Lake Lanier (Georgia) 38000 acres:: water volume 1,049,400 acre-ft severe drought 2007-2009

One inch of rain on the watershed in the summer had no effect on the lake level
Four inches of rain equaled a 1.4ft rise over five days

1�-2� of rain outta be real nice for Lewisville and Ray Bob. I�m excited!!!

Another question would be, how much colder will the water be after an all day cold rain event. I hope to know the answer to both tomorrow cause I'm going FISHIN'.

You're going to be disappointed.

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Just what falls in a lake directly? If we have an inch of rain in a rain gauge, it'd be something less than an inch as regards the rise in the lake itself. As water fills into a lake, from any source, its area expands. The more vertical the shoreline, the closer it'll be to a full inch. A lake with a rather flat sloping shore line will show the least rise.

Watershed and how much rain fell on it is a huge contributor, so are creek and river feeds. If not, we'd be in a heck of a tight spot: lakes in our area lose roughly 50" to evaporation over a typical year. If, say, in Ft. Worth the average annual rain is 30", we'd have a net loss of 20" or so per year.

Subtract another big number for what city water districts suck out of lakes and we'd be bone dry.

Watersheds, springs and other sources "funnel" a lot of water into lakes.

Brad

2" of slow soaking rain when it is this dry will be barely noticeable in RR. Better than nothing, but nothing to be excited about.

One rain event of this expected size won't typically make much of a difference, certainly when the watershed is dry and soaks up a lot of it, doesn't pass it down to the lake.

Lake Athens is up a bit . . . but the water went from being crystal clear all around my boat dock to chocolate milk. This will vary from lake to lake.

I'm going to watch. Theoretically, since Lake Athens is heavily spring fed, low water volumes fed into the lake by a major river system (it isn't on one), we might expect the ground water to "seep" into the lake over a period of days. Gravity and sandy soils. Hard to quantify as the city pumps water out for Athens residents.

Brad

Assuming an upstream lake doesn't release water into the lake in question, my experience is roughly 1:1 for dry ground and 3:1 for soaked ground.

I am pretty sure ground moisture before the rain event is the key factor.