Too much rain can cause ponds or pools to overflow. We must make sure you have adequate drainage, particularly in high rainfall areas (e.g. coastal regions, low lying valley areas). Heavy rain can also introduce impurities from roofs, walls, patios, and so forth – or pesticides and chemical fertilisers from garden soil.
Frequent rain may dilute nutrient availability, especially if the pond overflows. Although not usually a problem, persistent rain may disturb the pH balance of a pond – particularly acid rain.
Rain will re-invigorate a pond by oxygenating the water. Too little water, and ponds can quickly dry up in warmer weather unless you regularly top them up. Too much heat or wind, and they can also dry up due to evaporation. If the water level in a pond or pool is dropping fast you may suspect a leak, but this isn’t necessarily so.
You can test whether it is just evaporation as follows: Place a plastic container (e.g. bucket) full of water beside the pond or pool for a week (in same amount of shade or sun). Check how much the pool goes down compared with water loss from the bucket. If it is similar, you don’t have a leak.