Run-off from the Avoca River Basin. 145 



Effects upon the Permanence of the Streams. 



It is common knowledge in that district that the clearing of the 

 timber has most strikingly improved the summer flow of the streams, 

 by increasing the activity and duration of the springs. It is within 

 the writer's knowledge that the creek taking its rise in the granite 

 hills south of " The Gap," the highest point on the road from Avoca 

 to Ararat, and en the divide between the Avoca and Wimmera River 

 basins, wajs, prior to 1881, dry for the greater part of each summer. 

 Now it is a permanent stream, and even on April 19, 1922, was dis- 

 charging perhaps five cubic feet per minute. The same applies to the 

 Avoca and Glenlogie creeks at their junction below Amphitheatre, and 

 both were running freely on the same date. It was of interest to 

 note, too, that the two streams were there nearly equal, whereas prior 

 to 1880 the Avoca was much the larger whether under flood or summer 

 conditions. For this approach to equality, the cause is evidently the 

 greater recent reduction in the forest covering of the Glenlogie Basin. 



The deepening of the channels has had effects upon the extent of 

 the flooding. According to Mr. Ennis, an Amphitheatre resident, the 

 flats are now flooded less frequently and extensively than formerly. 

 This is due in all probability to the increased channel capacity which 

 also involves increased velocity. A proof of the latter was found by 

 inspection of the Avoca branch, coarse sand and gravels generally 

 being distributed very freely over the river flats and to an extent 

 obviously very injurious to their pastoral usefulness. This was not the 

 case formerly. 



In response to my request, the Postmaster at Avoca submitted 

 a number of queries to an old Avoca resident, Mr. Henry Brown, who 

 kindly answered them very fully. His statements agreed very well 

 with my impressions, except that he attributed the recent greater per- 

 manence of the river flow in summer to good spring rains and its occa- 

 sional failures to the water carrying capacity of the underground 

 drifts, which, if tested, he said, would show that the river never ceased 

 flowing at all. Floods, he said, came down more rapidly than for- 

 merly, for which he blamed the silting up of the large waterholes by 

 mining operations. Thousands of diggers had washed their dirt in 

 the river, and the Golden Stream Gold Mining Coy. had run thousands 

 of tons of " slum" from their puddlers into it. In places this slum in 

 the bed of the river was 5 ft. thick. The floods were also heavier than 

 previously, for which again he blamed the silting up by mining opera- 

 tions, causing lessened channel capacity. These siltings he also blamed 

 for various changes in the course of the channel. 



My observations of the changes in the country cover only a small 

 part of the Avoca's drainage area, but it is probable that they apply 

 with equal force to the whole area between the Avoca and the Pyrenees 

 which provides the chief remainder of the effective drainage areas, or 

 of a total of about 1000 square miles. 



The flow of the Avoca River is officially measured by the State 

 Rivers and Water Supply Commission at the Coonooer Weir, below 



