Actually that is already being done per a news report I saw some months ago.
Drones can use imaging to identify dry areas within the fields and that information is fed to the irrigation system. Actually goes a bit farther and can even likewise selectively apply fertilizers etc. during planting operations.
Thermal imaging depends on temperature differences. So the leak area may cooler if wet. Or if a puddle could get warmer if in the sun.
How the images appear depends on the devices and calibrations being used. Traditionally warmer areas trend to red and darker. Cooler areas go bluish. Matter of contrast overall.
So your project would need to include some parameters to identify, under varying conditions, what a leak may look like.
I can see a really neat project using a camera/camera app with thermal imaging capabilies, an area with dirt/sand etc. that you can moisten under varying conditions, place some thermometers for air and ground temperature readings, etc., etc.. Maybe a ladder (representing a drone in the air) from which to take the photographs.
Once you have photographs and temperature data collected then you will have an answer plus a good understanding of what all is involved.
Have fun with it.