Department of Health Library Services ePublications - Historical Collection Purpose To apply preservation treatments, including digitisation, to a high value and vulnerable Historical collection of items held in the Darwin and Alice Springs libraries so that the items may be accessed without causing further damage to the original items and provide accessibility for stakeholders. Reference and Research Disclaimer Please note: this document is part of the Historical Collection and the information contained within may be out of date. This copy is a reproduction of an original record. Please note that the quality of the original record may be poor and cannot be enhanced with the scanning process. Northern Territory Department of Health Library Services Historical Collection 0 0-7,::;_ 7 HISTORICAL COLLECTION ""€ NT DEPARTMENT OF HEALTH I -~ l ~ AND COMMUNITY SERVICES ·la..- j ~ .. ~ '~ .. ' .. • t. ;., :· .. : ,... ... '! ..- • ..._._.( .....' . :-. !. MEDICAL ENTOMOLOGY INVESTIGATION •' . {:~ OF PROPOSED JUNCTION WATER HOLE DAM ON THE TODD RIVER ""-. •'So ti : t i r• ..: I.• l • '• . ' "ii -' • ~ • I ' . ' ' ' I ( I • ~ • • ~ I I~ 't I!' ~. • • • ·1, J ~ • :. • .'.!. ', ,, . r • I •/, l ·~. • •..... "·,1 '). I .} ...1. .,' • : • I J l• ".• ·, it, ! ·•,, 1 f ~.. ; ...... ' . ,,._ For more Information Contact: ' '' I j,t 1· Department of Health and Community Services : 'I• Medical Entomology Branch GPO Box 1701 •I ' DARWIN NT 0801 • I Telephone 22 8333 Peter Whelan Senior Medical Entomologist , .. 'DLHIST 614.4323 .J WHE 'i 1990 ,.. I 1l1[1l1~11i1 ~lllf1111ij1i 1111]1i11~1111 ~1~1ij 111111~11 3 oa20 00019002 o 1':3~() MEDICAL ENTOMOLOGY INVESTIGATION OF PROPOSED JUNCTION WATERHOLE DAM ON THE TODD RIVER . PETER WHELAN SENIOR MEDICAL ENTOMOLCGIST MEDICAL ENTO'v10LCGY BRANCH NORTHERN TERRITORY DEPARTMENT OF HEALTH AND COMMUNITY SERVICES MARCH 1990 TABLE OF CONTENTS PAGE 1. 0 BACKGROUND 1 2. 0 FIELD INVESTIGATIONS 1 2.1 Aim 1 2. 2 Surface Water Survey 1 2. 3 Larval Sampling Method 1 2. 4 Adult Sampling Method 2 3.0 RESULTS 2 3. 1 Surface Water Survey 2 3. 2 Larval Sampling 3 3 . 3 Adult Sampling 4 4. 0 DISCUSSION 5 4 . 1 Present Mosquito Breeding Habitats 5 4. 2 Potential Mosquito Breeding Habitats 6 4. 3 Potential Public Health Problems 8 Posed by Biting Insects 4.3.1 Epidemic Polyarthritis 8 4.3.2 · Australian Encephalitis 8 4.3.3 Malaria 8 4.3.4 Nuisance Insects 8 5. 0 MEASURES TO REDUCE OR AVOID MOSQUITO BREEDING 9 5. 1 Design Features 9 5. 1 . 1 Fish Transfer 9 5. 1 . 2 Stock Exclusion 9 5 .1 .3 Water Level Manipulation 9 5. 1 . 4 Sediment Traps 9 5. 1 . 5 Prevention of Leakage 9 5. 2 During Construction 1 0 5. 2. 1 Vegetation Removal 1 0 5 .2.2 Flotsam Removal 1 0 5 .2. 3 Mosquito Monitoring 1 0 5.3 After Construction 1 0 5 .3. 1 Prevention of Nutrient Input 1 0 5. 3. 2 Weed Control 1 0 5. 3. 3 Flotsam Removal 1 0 5. 3. 4 Larval Mosquito Control 1 0 10/12/90 TABLE OF CONTENTS (continued) PAGE 6.0 MONITORING OPERATIONS 1 1 6. 1 Adult Mosquito Monitoring 1 1 6. 2 Downstream Habitat Monitoring 1 1 7.0 CONCLUSION 1 2 7. 1 Present Mosquito Breeding 1 2 7. 2 Potential Mosquito Breeding 1 2 7. 3 Public Health Effects 1 2 7. 4 Measures to Avoid or Reduce Mosquito Breeding 1 2 7. 5 Mosquito Monitoring Programme 1 2 8. ACKNOWLEDGEM EN1S 1 2 MAPS 1 Mosquito Larval and Adult Sample Points - Damsite Area 1 3 27/2/90-7/3/90 2 Mosquito Larval and Adult Sample Points - External to Damsite 1 4 27/2/90-7/3/90 TABLES Larval Sample Results 1 5 2 Adult Mosquito Collections 28/2/90 and 1/3/90 1 7 APPENDIX / Photo 1 - Damsite looking downstream above adult trap 1 9 site (4) & (9) Photo 2 - Close up of a rock pool showing Anopheles larvae at 1 9 I a rv a I s amp I e poi n t ( 4) Photo 3 - General view of Erewe Thele, near adult trap site (8) 2 O Photo 4 - Downstream of damsite near adult trap site (10) 2 0 Photo 5 - Damsite in the bed of the Todd River at trap site (4) 2 1 Photo 6 - Upstream of Junction Waterhole near larval sample point (5) showing Typha reeds at margin 2 1 Photo 7 - Carbon dioxide baited EVS light trap below damsite at 2 2 adult trap (9) Photo 8 - Upstream of Wigley Waterhole at adult trap site (6) 2 2 Photo 9 - One of the Wigley Waterholes between adult trap 2 3 site (5) and (6) showing Typha reeds at RHS margin I I Common Mosquitoes in the Northern Territory - Description 24 of Species, Habitats and Disease Potential II I Mosquito Species Recorded from Alice Springs Area 30 IV Monthly Max. Numbers of Adult Female Mosquitoes per CO2 Trap-Night at Site "A", II Parpa Swamp, Alice Springs 1989 3 1 MEDICAL ENTCMOL03Y INVESTIGATION Q£ PROPOSED JUNCTION WATER .!::iQLE DNv1 Qbl THE TODD RIVER MEDICAL ENTOMOLCXW BRANCH MARCH~ BACKGROUND The Power and Water Authority is examining preliminary information for a possible flood mitigation dam at the Junction Water Hole on the Todd River near Alice Springs. An engineering consultant's report in May 1989 found no engineering factors precluding construction of a dam at the Junction Water Hole and suggested feasibility studies be undertaken, including environmental constraints. Previous investigations for purely recreational lakes undertaken in the Alice Springs area included feasibility studies of Emily Creek in September 1985 and an environmental review for a dam on the Todd River in 1981. The latter report mentioned the possibility of an increase in mosquito borne arbovirus activity. The former report outlined the need to consider arboviruses and to prevent new mosquito habitats. In January 1990 the Power and Water Authority approached the Department of Health and Community Services requesting a Medical Entomology investigation of the Junction Water Hole site to report on the present and potential biting insects and to assess the likely impact of a dam on insects of public health importance. The Medical Ent9mology Branch conducted a field investigation of the site from 27 February 1990 to 1 March 1990. This report outlines the results of the field examination and conclusions on the impact of a dam in respect to biting insects. 2.0 FIELD INVESTIGATIONS 2.1 Aim The aim of the investigation was to determine the species of mosquitoes present at the dam site and in the general vicinity, together with a measure of their abundance and their specific breeding sites. This information and other field observations would then be used to assess and report on the likely impact of the dam with regard to potential pest and public health problems posed by biting insects. 2.2 Surface Water Survey A surface water survey was carried out both upstream and downstream of the proposed dam site at Junction Water Hole to determine the present characteristics of any pools and the extent of surface water. Observations on the physical and biological characteristics were noted, including water depth, edge substrate, presence of vegetation, and the presence of relevant/aquatic life other than mosquito larvae. 2.3 Larval Samplinq Method The mosquito larval survey was conducted in the vicinity of the proposed dam site and a number of selected sites along the Todd River including Wiggleys Water Hole, the Telegraph Station and Heavitree Gap. Wiggleys Water Hole represents the more permanent natural pools in an undeveloped area receiving considerable recreation use , the Telegraph Station represents a sandy river bed receiving seepage and nutrients from a developed recreation area, while Heavitree Gap represents a sandy river bed receiving waste water via storm water drains from an urban environment. Larval sampling was carried out with the aid of a standard larval dipper at selected or prospective habitats. A number of dips were taken at each site to determine the average number of larvae per dip and the growth stages (instars) of larvae present. Samples were only taken from pools representing the different habitats in one area. Larvae were collected alive and transferred to 70% alcohol at the end of each day. Selected samples were reared to adults. All larvae or reared adults were identified in the Medical Entomology laboratory in Darwin. 2.4 Adult Sampling Method Adult mosquito populations were sampled with dry ice (carbon dioxide) baited EVS light traps, which are standardized mosquito sampling devices widely used in Australia. Trap locations were chosen to sample populations near surface water habitats at the time of the survey. Traps were set at chest height before sundown and operated all night. Trap collection was between 7 and 8 am the following day. Traps were located as close to the river as possible and next to vegetation. All collections were sorted and identified on the day of collection, with reference samples taken for checking and inclusion into a reference insect collection at the Medical Entomology Branch in Darwin. 3.0 RESULTS 3.1 Surface Water Survey There were many pools in the bed of the Todd River from Erewe Thele to Heavitree Gap (See Map 1 ). Photos of the various habitats is shown as Appendix I. The pools near Erewe Thele included relatively large deep pools with discrete sand or rock margins. The shallow downstream edge contained a few small cut off pools. Between Erewe Thele and Junction Water Hole there is a 300 metre stretch of rock and sand pools with minor amounts of algae on rock surfaces below the water. A few pools had small stands of Typha reeds, but otherwise they were vegetation free and with relatively clear cool water.