EIS 1483 AA0681 11 Water quality in the Snowy River catchment area : report on 1996/97 data; nutrient loads in the Thredbo river; trend assessment NSW YEPT PRIMARY IRDUSIRIES I AA0681 11 I LAND &WATER CONSERVATION I I I I I I d I I I I I I I I NSW Department of Land and Water Conservation I I I DEPARTMENT OF LAND & WATER CONSERVATION CENTRE FOR NATURAL RESOURCES I I I WATER QUALITY IN THE SNOWY I RIVER CATCHMENT AREA I - Report on 1996/97 Data - Nutrient Loads in the Thredbo River I - Trend Assessment I I I I I I I I H I I DEPARTMENT OF LAND & WATER CONSERVATION CENTRE FOR NATURAL RESOURCES WATER QUALITY IN THE SNOWY RIVER CATCHMENT AREA - Report on 1996/97 Data - Nutrient Loads in the Thredbo River - Trend Assessment Zenita Acaba, Lee Bowling, Lloyd Flack June 1998 and Hugh Jones CNR 99.005 [s9697co2.Doc] CENTRE FOR NATURAL RESOURCES © Department of Land & Water Conservation ISBN 0 7347 5023 4 Public Document Water Quality in the Snowy River Gatchinent Area, 1996197 Report 1 I I I I I I Cologne I In KOln, a town of monks and bones, I and pavements fang'd with murderous stones I and rags, and hags, and hideous wenches; I counted two and seventy stenches, I All well defined, and several stinks! I Ye Nymphs that reign o'er sewers and sinks, The river Rhine, it is well known, I Doth wash your city of Cologne; But tell me, Nymphs, what power divine I Shall henceforth wash the river Rhine? Li I Samuel Taylor Coleridge, 1828 I I I 1 Water Quality in the Snowy River Catchment Area, 1996/97 Report I I I ACKNOWLEDGEMENTS The majority of the sampling for this project was undertaken by staff of the Snowy Mountains Hydro-Electric Authority's Hydrographic Office at Jindabyne, chiefly by Messrs. Phil Boreham, I David Whitfield and Jason Venables. The staff of the Hydrographic Office were also principally involved in the setting up of the automatic water quality samplers and flow gauging stations at the I sites within the Thredbo River subcatchment, which enabled event sampling and load estimates for the project. I We acknowledge the input of Messrs. Ken Jones and John Denham, of the Snowy Mountains Hydro-Electric Authority, for the co-ordination of the SMII-IEA's input into the project, and for I review of this report. We also acknowledge the continued interest in the project, and in the protection and improvement of water quality in the Snowy Mountains area through total catchment management, of Messrs. I Barry Dunn and Tony Gan, of SMHEA's Operations Planning Division. They are also thanked for their review comments on the report. I Mr Tom Freece of SMHEA is thanked for providing river flow data for the project. I Sample analysis was undertaken by the Department of Land and Water Conservation's Water Environment Laboratory at Arncliffe. I Finally, we wish to thank Mr Brett Miners of DLWC Cooma (Snowy-Genoa Water Resource Manager), who reviewed the initial draft of this report. I I I I I I I I I V Water Quality in the Snowy River Catchment Area, 1996/97 Report I I I SUMMARY The water quality of Lake Jindabyne and the streams within the upper Snowy River catchment I area was generally good in 1996/97. The lake continued to have low to moderate concentrations of nutrients, and low conductivity and turbidity, as in previous years. There was some oxygen depletion of the deeper waters during summer and autumn whilst the lake was thermally stratified. I There was little algal growth within the reservoir. The Thredbo River continued to have the best water quality of the three major inflows to the lake, I with low nutrient concentrations and turbidity. The Mowamba Aqueduct had the poorest water quality of these inflows in 1996/97, with Wollondibby Creek being only slightly better. Both had total phosphorus concentrations in the moderate range, and slight turbidity. However, in terms of I nutrient concentrations, all three inflows still met ANZECC (1992) water quality guidelines for the protection of aquatic ecosystems. I Nutrient concentrations and turbidity at the six sampling sites in the Thredbo river subcatchment upstream of Paddys Corner were low during base flow periods, but increased during storm events. I Nutrient loads increased with distance downstream from Deadhorse Gap. Areal load estimates indicate high input of nutrients from the catchment area between Bundilla and just downstream of the Little Thredbo River confluence. This area, which comprises only 1.5% of the area of the I Thredbo River catchment upstream of the Little Thredbo River confluence, was estimated to contribute approximately 24% of the total phosphorus load entering the Thredbo River upstream I of this point, and 2 1 % of the total nitrogen load. Nutrient input from the Little Thredbo River subcatchment was the lowest of any part of the Thredbo River catchment. Impacts from the Lake Crackenback resort were indicated as being I negligible, and there was very little difference in the nutrient input from the Thredbo Village and ski slope area compared to other undeveloped areas of the catchment. Unfortunately the frequent I failure of autosampling equipment at Paddys Corner prevented a number of high flow events from being sampled there, leading to unreliable load estimates in comparison to the other sites. For this reason, nutrient inputs to the Thredbo River from the section of catchment between the Little I Thredbo River confluence and Paddys Corner could not be adequately calculated. The nutrient loads estimated in this study for the entire Thredbo River catchment area were similar I to those calculated in an earlier study by Bowling (1992). Total phosphorus loads exported from the catchment in terms of kilograms per hectare per year were found to be higher than those I reported in the literature for other forested areas of south-east Australia. The high rainfall of this alpine area, much of which falls as snow which captures airborne particles containing phosphorus, has been proposed as the main reason why the Thredbo River annual areal total phosphorus load I coefficients are higher than those measured elsewhere. Areal total nitrogen load export coefficients were also more similar to those reported from urban catchments than for forested catchments. I Trend assessments were also carried out using nutrient and turbidity data collected at sites where a minimum of at least five years routine water sampling had been undertaken. These sites included Paddys Corner and others upstream on the Thredbo River; Wollondibby Creek at Gunnadoo; I Mowamba Aqueduct at its Lake Jindabyne outfall; Perisher Creek at Blue Cow; and the Snowy River at Dalgety. No trend was apparent in total phosphorus and total nitrogen concentrations at Water Quality in the Snowy River C'atchment Area, 1996/97 Report 111 I I any site, even after the data had been flow adjusted. However, many sites on the Thredbo River indicated significant increasing trends in turbidity over the period 1992 to 1997, although turbidity was still very low. I A range of recommendations have been suggested for catchment management purposes, and for the protection of water quality in the area, which remains amongst the best of anywhere in New South I Wales. Routine monitoring of selected sites should continue, to enable better estimates of long term trends in water quality at these locations. However, further nutrient load studies of the Thredbo I River catchment are not seen as a priority, unless carried out for a specific purpose such as monitoring the impacts of further development in the valley, monitoring the results of remedial action recommended from this study, or determining inputs from the section of catchment between I the Little Thredbo River confluence and Paddys Corner. Possible nutrient load studies on Wollondibby Creek and the Mowamba River have been mooted, I but a decision needs to be reached on environmental flows in the Snowy River downstream of Jindabyne Dam before it is decided whether these studies should proceed or not. This decision will influence the ultimate destination of Mowamba River water, that is, whether it will continue to be L diverted to Lake Jindabyne, or flow directly to the Snowy River, and will therefore be a factor when applying for future funding of water quality studies of the Mowamba River. I A closer alignment of the water quality monitoring being undertaken throughout the catchment and the requirements of the Snowy-Genoa Total Catchment Management Committee is urged, with increased input and direction from the TCM process. Better documentation and co-ordination of all water quality studies in the area is also desirable, and the involvement or funding assistance in future studies from all agencies with an interest in the water quality of the area is encouraged. I Only in this way will the good water quality of the area be maintained into the future, and the need for subsequent remedial action avoided. I I I I I I I I iv Water Qualily in the Snowy River Catchment Area, 1996/97 Report I I TABLE OF CONTENTS i. INTRODUCTION..............................................................................................................................1 I 2. BACKGROUND ................................................................................................................................ 1 3. OBJECTiVES OF THE STUDY....................................................................................................... 2 I 4. FUNDING ARRANGEMENTS......................................................................................................... 3 5. SAMPLING PROGRAM...................................................................................................................3