OWENMORE RIVER U Proposed Arterial Drainage J Environmental Impact Assessment
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'-1 u OWENMORE RIVER u Proposed Arterial Drainage J Environmental Impact Assessment LJ Botanical and Ornithological Surveys u A Report for National Parks & Wildlife Service Office of Public Works J 7 LJ 7 Li Roger Goodwillie, Philip Buckley & J Caitriona Douglas 1992 j PREFACE J J This report is the outcome of a contract with theWildlife n u Service to evaluate the vegetation and birdlife of the Owenmore catchment, County Sligo, and to assess the impacts on rl J them of a proposed arterial drainage scheme. The study was carried out in 1988-89 under the supervisionof Jim Ryan who also gave some assistance in the field.The personnel involved were: i Roger Goodwillie final report and botanical survey Philip Buckley ornithological survey J Caitriona Douglas botanical survey ri Enda Mooney botanical field assistant 1988 u r-1 Wewould like to acknowledge the help of several local J naturalists, P.Timpson,D.Cotton, S.Perceval, J.Crichton and J B.Jobson and the many pleasant landowners we met in thefield. J.Martin and J.Howard of the Arterial Drainage Section, Office of Public Works were also of considerable assistance. n u u t:i 0 CONTENTS 0 Preface & Acknowledgements SECTION 1 - INTRODUCTION Page 0 1.1 Description of Catchment 0 1.2 The Rivers 1.3 The Lakes 1.4 Arterial Drainage 0 1.4.1 Previous schemes 1.4.2 Present proposals 0 SECTION 2 - WILDLIFE SURVEYS 0 2.1 Botanical Survey 9 2.1.1 Results 14 2.1.1.1 Swamp vegetation 15 0 2.1.1.2 Tall Grass vegetation 18 2.1.1.3 Short Grass vegetation 20 2.1.1.4 Peatland vegetation 23 2.1.1.5 Woodland vegetation 27 0 2.1.1.6 Tillage 28 2.2 Ornithological Survey 28 0 2.2.1 Winter 28 2.2.1.1 Site counts 28 2.2.1.2 Road transects 32 2.2.1.3 Foot transects 35 0 2.2.1.4 Winter bird populations 39 2.2.2 Breeding season 41 1J 2.2.2.1 Wader survey 41 2.2.2.2 Lough Arrow 43 2.2.2.3 Other habitats 44 D 2.2.2.4 Summer bird populations 48 SECTION 3 - EVALUATION OF WILDLIFE 0 3.1 Vegetation 49 3.1.1 Species rarity 49 3.1.2 Vegetation rarity 55 3.1.3 Species diversity 55 3.1.4 Habitat diversity 57 3.2 Birdlife 57 3.2.1 Winter 59 0 3.2.1.1 Wildfowl and waders 59 3.2.1.2 Other wintering populations 59 3.2.2 Breeding season 61 0 3.2.2.1 Waders 61 3.2.2.2 Lough Arrow 64 0 3.2.2.3 River channels 64 3.2.2.4 Other habitats 64 3.3 Areas of Scientific Interest 70 3.3.1 Unshin River 70 I 3.3.2 Lough Arrow 76 U 3.3.3 Ballysadare Bay 79 3.3.4 Flughany Bog 84 3.3.5 Doocastle Turlough 86 I tJ 3.3.6 Templehouse/Cloonacleigha Lough 89 3.3.7 Cloonakillina Lough 95 3.3.8 Lough Meharth 97 3.3.9 Quarryfield West Turlough 100 3.3.10 Turloughmore 102 3.3.11 Ballygawley Lough 104 3.3.12 Corhawnagh 106 3.3.13 Carrownabunny 108 3.3.14 Knockmullin 110 3.3.15 Feenagh/Bunnamuck L. 112 3.3.16 Lough Dargan 114 3.3.17 Fin/Risheen Loughs 116 3.3.18 Greenan 118 SECTION 4 - IMPACTS OF PROPOSED DRAINAGE 121 4.1 Impact on vegetation 122 4.1.1 Vegetation diversity 128 4.2 Impacts on species 128 4.2.1 Plants 128 4.2.2 Birds 132 4.2.2.1 Aquatic species 132 4.2.2.2 Terrestrial species 134 4.2.2.3 Significance 136 1 4.3 Impact on Areas of Scientific Interest 138 (ordered as above) J SECTION 5 - CONCLUSION 147 6. REFERENCES 149 1 7. PLATES 1 - 37 152 APPENDIX 1 Vegetation types 160 M APPENDIX 2 Sites of high vegetation diversity 200 U 1 d SECTION 1 INTRODUCTION 0 0 1.1 DESCRIPTION OF CATCHMENT 0 The Owenmore catchment covers some 65,500 ha which is predominantly in Co. Sligo but with small extensions into Mayo andRoscommon (Figure 1). It is boundedby the Curlew 0 Mountains (264m) on the south side and the Ox Mountains(514m) on the north and north-west. The eastern edge is markedby the low hills above Lough Arrow and the western by theridge north of Tobercurry.The catchment is divided into three obvious 0 sections by its threetributaries: the Owenbegflows east along the foot of the Ox Mountains,the Owenmore northwards through the centre of the catchment and the Unshin north-west 0 from Lough Arrow. The geology of the area is relatively simple in thatall the low land is of limestone (Upper Carboniferous- Visean) which 0 also builds the hillsofKeshcorran and Carrowkeel beside Lough Arrow.Older rocks rise through the limestone in two parallel ridges, the Old Red Sandstone of the Curlew Mountains lJ and the precambrian gneiss and quartzite of the Ox Mountains. Glacial till covers much of the low land (Figure 2)so that 0 the underlying rock is seldomseen. The till is thickest between Ballymote and the Curlew Mountains where it is formed into numerous drumlins,the western end of the main drumlin belt that runsthroughCavan, Monaghan and Down. Till is 0 absent from most ofthehill areas and from the low-lying ground about Tobercurry. It is thin also near the centre of the catchment,for example,on the hills north of Ballymote 0 and on each side of Riverstown. The basement rock isactually exposed in a low-lying area around Lough Dargan, perhaps asa 'drift-shadow' in the lee of the Ox Mountains. 0 Peat is widespread in the catchment,and occurs on all the mountainsincluding the limestoneCarrowkeel, and in many parts of the lowlands. It is particularly prevalent in the 0 Owenmore sub-catchment where it fills the inter-drumlin hollows, the river valleys and the flat land near thethree major lakes- Cloonakillina,Cloonacleigha and Templehouse. 0 There is a significant amount of peat in the Owenbegvalley also, part of which is associated with river sediments,but rather little in the Unshin. 0 Soil types (Figure 3)are related both to peat content and to the physical quality of the glacial till which is generally fine-grained and rich in clay. There are small areas ofbrown 0 podsolics/brown earths at the edges of the catchment andon the hilllimestones,with patchesof well-drained skeletal soils at the foothills of the Ox Mountains. Otherwise gley 0 soils predominate with grey-brownpodsolics generallyon higher ground and peaty gleys or basin peats in the depressions. The most frequent soil type in the affected land is probably a peaty gley characteristic of the floodplains of EJ 0 1 j n Figure 1. Map of the Owenmore River divided into itssub-catchments J z 0 0 0 0 0 Figure 2. Surface geology of the Owenmore catchment 0 0 0 0 0 0 0 0 Peat/alluvium Till-free Limestone till 0 0 0 0 0 3 J J J J ® Blanket peat ® Basin peat/cutover ® Gleys & peaty gleys MOther gley soils Skeletalsoils Podsols & brown podsolics Brown podsolics/brown earths Grey-brown podsolics J Alluvium/peat (parent material) Figure 3. Soil types in the Owenmore catchment 4 0 the larger rivers.(The term 'affected' land is used in this 0 report in preference to 'damaged' or 'benefitting' land.Its counterpart is 'unaffected' land). 0 1.2 THE RIVERS 0 The catchment is notable for the very different characters of its three major branches.The Owenbeg (23 km) isan acid mountain river subject tospates. Its banks are relatively IJ high and,in the lowlands, often tree-lined. It has a gravel bed and a reasonable gradient and is very seldom polluted.The Owenmore (52 km)is a neutral river, flat, slow-moving except 0 at Annaghmore and partly channelised by previous drainage. It is generally eutrophic receiving both agricultural and creamery effluents.Recent changes at Achonry creamery have 0 led to a decline in nutrient levels (Timpson pers. comm.).The Unshin (23 km) is an alkaline river, rising in thespring-fed Lough Arrow. Its pH remains high throughout its length butit becomes more nutrient-rich as it approaches Collooney. Much of 0 its length is slow-moving but it has two steeper stretches, one with rapids above Lisconny and the other in Markree. 0 The Owenbeg joins the Owenmore above Collooney where a series of waterfalls occurs behind the town. The Unshin comes injust below and they flow northwest through the Collooney Gap inthe 0 Ox Mountains to Ballysadare. Another waterfall takesthe river into the muddy Ballysadare Bay where it meanders tothe sea.Two minor streams enter the Owenmore between Collooney and Ballysadare taking drainage water from the northern slopes 0 of the Ox Mountains. The stream and river channels total 312 km in theOwenmore 0 sub-catchment 211 km in the Unshin and 99 km inthe Owenbeg. A stream order analysis (Table 1) gives a good impression ofthe size of channel. First order streams are those flowing from the various sources, springs or bogs. Where two first order IJ streams meet, the flow becomes a second order stream andwhere two seconds meet, a third order, etc. 0 TABLE 1 Length (km) of each stream order in the Owenmore system. a Stream Owenmore Unshin Owenbeg Greater Total Order Owenmore 0 1 165 129 60 7 361 2 70 44 17 2 133 3 39 24 4 - 67 0 4 38 14 18 - 70 5 - - - 8 8 0 Total 312 211 99 17 639 Note: The greater Owenmore is that river plus its tributaries below the confluence of the Unshin at Collooney.