water in ponds and wells much reduced in summer give reason
Answers
Answer:
The water level in a well is the position of the water table, the upper surface of the groundwater. In turn, most ponds are connected to the water table, meaning that the elevation of their free surface ( = their stage) coincides with that of the surrounding groundwater.
So the question really becomes: Why does the water table fluctuate up and down through the seasons?
In temperate areas, groundwater typically loses water continuously to streams and rivers. These are located in the lowermost areas of the landscape, so that the water tables slope towards them. This is why streams still have a flow or discharge in them, even after months without any rain. This low flow in rivers, contributed by the groundwater during the dry season is called baseflow.
In order to gain water, you need groundwater recharge: this is part of the water that infiltrates into the soil during and immediately after rainfall events, when it is able to keep going down into the soil, vertically (this is called percolation), until it hits the water table, thus recharging the groundwater.
Let’s now compare how groundwater gains water versus how it loses it: The gain (recharge) only happens when the whole soil profile is wet enough to transmit water that infiltrates at its surface all the way down to the water table. This typically happens during the wet season of the year, and it will take a few storms at the beginning of it before it can happen. In conclusion, recharge only occurs during and after rainfall events, when you already are well within the wet season (the time of the year when it rains more).
On the other hand, the loss of groundwater to the streams is more or less continuous, year-round. As groundwater loses water, that feeds the streams, the water table will go down by a little bit every day (typically, in the order of 1 mm to 1 cm per day).
Final result is that the water table will go up during the wet season, when recharge is happening and there is more input to than output from the groundwater. It will reach its seasonal maximum towards the end of the wet season. Then, as soon as the wet season ends, it will start decreasing, as there is now only loss but no further gain (until the next wet season). The seasonal low of the water table - accompanied by lowest levels in wells and ponds connected to the groundwater- will happen at the end of the dry season/beginning of the wet season.
I assume you are writing from the perspective of somebody who lives in an area where the summer is the dry season.
As somebody else already answered, evaporation might also be important for understanding pond levels, but if a pond is connected to the surrounding groundwater, its free surface will be at the elevation of the water table.