Three side walls gradient should have been more like 45 degrees angle. And one side with a 15 degree angle where one can walk into the pond. Right now the sidewalls looks somewhat like a 75 degree angle.
Even in this pond you can let it be as-it-is and let nature take its own course. Only concern is one edge is very close to the fence which might cave in if the soil got too moist.
Putting liner will not harvest rainwater it will just act as a holding tank. Thus the well-water table will keep going lower. The usefulness of the pond is to send rainwater into the ground as it just did (in the pics). The soil erosion will reduce with time as vegetation grow on the sloping sides.
There was another question I received in email:
Question: “Dug a pond -21 ft by 15 ft by 9 ft depth a year Plus Back. I have a borewell 400 Ft deep almost 1.5 m from one end of the pond and a 5KW/5HP Solar Pump. The land which this system covers is only 1.75 Acres and no plan to buy anymore. Is it a good idea to not use pond liners and allow it to be filled with Rain water–During summer it is very Dry–Our Pump output is reasonable but not high. I want to exploit the monsoon so that we can build a water table. Will this also help in recharging the Borewell” ?
Answer: Surely using pond without a liner will help to recharge the borewell. You could have connected the roof top rainwater directly into the borewell too using a cloth filter to remove bird-dropings, leaves and twigs.
The closeness of the pond to the borewell should not deteriorate the quality or quantity of bore-water. In fact putting rainwater into the bore directly or via nearby pond will improve the quality of the bore-well-water.