I am building a house near Idyllwild California elevation 4,600ft. USDA z8b (4 seasons, some but not much snow and rains only in winter) with very sandy soil.

OK the dream is to have a gold fish pond that also act as a very small reservoir to collect winter rainfall. I am thinking of a 5ft avg deep pond with footprint of 15ft x 15ft during dry season. The same pond swell to 25ft x 25ft and 6.5ft deep or so during rain/snow season. I would like to pump water from the pond for irrigation during the dry seasons, then refill the pond with fresh tap water and maintain the 15ftx15ft at 5ft deep.

Question:
Being very sandy, and the top shores will be exposed to sunlight for months. what would be best way to build this pond? No bottom drain right? Being a mud pond, how to keep the pond relatively clear?

Any advice and suggestions are welcome and appreciated