Water catchments need clay soil. Sandy soil will allow water to leak. (This is fine as a step in groundwater recharge, but no food for a catchment.)
Don't dig new water catchments without knowing about the soil underneath. Expanding existing water catchments may be a better idea.
Find out where the clay layer finishes, and don't dig past it. If you do, or there is any leakage, use more clay to patch it.
Where evaporation is high, water catchments should be deeper and narrower. Shallow and wide means more water lost to evaporation.
Look at water quality as well as quantity. E.g. use a sedimentation trap or settling pool to allow sedimentation, reducing solids (including soil and animal waste). An infiltration well is a useful step in improving water quality.
Manage the catchment. Look at inlets and the catchment area.
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