A: That's a problem, for sure! Let's take a look at some reasons why your water level is dropping below your skimmer opening in the first place. One of them could point to your solution.
Reason #1: Wrong Pump Size
Skimmers are rated for maximum water flow. If your pump exceeds this rating, the water will leave the skimmer faster than it enters—and you'll be left with a low water level. Check your pump to be sure it's sized correctly for your skimmer.
Reason #2: Accumulated Debris
Is your skimmer's filter mat plugged? Nets and media pads catch a majority of debris as the water passes through your skimmer (which you then clean out several times a year), but some of it may fall to the bottom. That debris could then plug your filter mat and prevent water from getting to your pump. It could also cause a water backup, allowing water to escape from other areas of your pond. When you pull out your filter pad, check for debris buildup in the skimmer bottom.
Reason #3: Skimmer Height
If your skimmer is set at the wrong height, that could cause problems, too. It should be set so that the natural water line of the pond when filled is about an inch below the top of the skimmer opening. If it's set where the water level is lower, small fluctuations in the water level can make a big difference. Check your skimmer height and adjust as needed.
Reason #4: Too-Low Overflows
If you installed an overflow in your skimmer, make sure the overflow's bottom is not lower than where the water level should be. Otherwise, you will have issues when you have small fluctuations in your pond's water level. Check to be sure any built-in overflows are positioned at the right height to allow water to drain from the skimmer.
Reason #5: A Leak
Dropping water levels could indicate a leak, so check around your pond for pooling water. Here, we outline in detail how to find and repair a leak.
Reason #6: Evaporation
The sun's evaporation power can play a role in your waning water levels, too. If this becomes a problem over time, you can install an auto-fill valve to refill your pond when it gets low. At the very least, install an automatic shutoff switch; if water depletes to a certain point, the pump will switch off automatically.
Good luck figuring out this mystery!