I have visited the Maniototo region and managed to visit the Blue Lake which was actually green from recent rain.  The Blue Lake is located at St Bathans and was formed by sluicing the surrounding area for gold over 100 years ago.  The region has many artifacts and constructions resulting from gold mining activities including water races many kilometers in length hewn around the hillsides by miners and chinese navvies who were employed to construct them.  These fed gold mining activities away from the water source in the mountains.  Many of them are still in use today to provide much needed irrigation in a historically low rainfall area.