The water in the bowl was adequate previously, because the leaking flapper was keeping it full. The small refill tube is either not sending any water to the bowl through the overflow pipe, or is is not sending enough. You will have to check it to see if an adequate amount is comng out of the tube and going down the overflow pipe.: My old flapper was leaking. I replaced it with a new one and ever since the water level in the bowl is very low. The water empties out and the flapper closes long before the toilet completes the flush. I have changed to other flappers but with no improvement. Nothing I have tried works.