Just to be clear, TDS is NOT Total Dissolved Salts, it IS, Total Dissolved Solids. Usually, TDS is comprised of calcium, sodium, potassium, phosphates, nitrates, chloride and a thousand other orgnanic and inorganic molecules. The OP mentioned "brine" so I ASSumed his main Dissolved Solid was sodium/chloride. There is no way to calculate salinity from a TDS reading. If I knew the electrical conductivity of the water and a few other parameters, I could guesstimate the salinity.

Desalination in large quantities is ridiculously difficult and energy consuming. When you have a closed system, like a pond, salinity will exponentially increase via evaporation. Do you know how the salt on your table is made? Evaporation of shallow, large surface area sea water ponds like the OP is proposing.