Before the locks were built the River  varied from very low flows to full flood levels. The paddle steamers couldn't navigate  a very low river, and so barges loaded with wool, wheat and other goods sometimes stood for months before being able to move. 


After the locks were completed water levels could be maintained.  This is the same section of cliffs taken many many years later.


Lock 5 after completion.  Regulated river levels meant irrigation pumps could operate year round, as could river steamers.


Lock weir for regulation of water flow.  Lock chamber for allowing navigation.


In the 1920 & 30s, it was common to go up river on picnic days and weekends.  Numerous pleasure launches from those years have now been replaced with houseboats