Could be the same one after a rain, it had a concrete silt hole before the main dam, a cement sill around the top that directed water down the corners to avoid scouring the slope and a dry well with a horizontal pipe from the dam floor, this kept the windmill pump primed.
Mr Liebe beside the well, all of his projects were built to this standard.
kenny-mopar, Mr Liebe took up this land at Wubin WA in 1908, this photo is about 1926 as the second house appears to be under consruction. The completed dam is nearby. End of shed was living quarters for workmen. Cheers David.