Cregduff
| Location: | Near Ballinrobe, Co Mayo |
| Size: | 2,998 ha |
| Farming: | Grassland beef and sheep production |
| Soils: | Free draining shallow soils over karstified limestone |
| Rainfall: | 1,200 mm |
Weather - Cregduff East Weather - Cregduff West
The Cregduff catchment is estimated to be 2,998 ha in area. Grassland makes up 92% of the landuse with only 1% arable and the rest in non-agricultural use. It was chosen to represent areas of free-draining, shallow soils over karstified limestone. The karst landscape as found in Cregduff is typical of much of the area which contributes groundwater to the three large western lakes - Loughs Corrib, Mask and Carra. Groundwater pathways predominate in this type of landscape and there is little or no surface drainage given the free-draining nature of the soils and the underlying karstified limestone with its network of fissures and conduits. The Cregduff spring, which is used to supply water to the local community, was selected for monitoring based on water quality and discharge data collected by the EPA.
Dolines and swallow features are prevalent here, as dissolution of the underlying bedrock proceeds, leading to collapse and depressions at the soil surface. The area has many turloughs or seasonal lakes which fill up during the winter and recede each year in the spring as the water table falls.
The western half of the catchment, closest to the spring, has shallow soil, mostly less than 3 m deep, where the epikarst is often exposed to the surface. The eastern half of the catchment has somewhat deeper soils with brown earths and brown podzolics on the head slopes and typical and humic rendzina soils on the hill slopes and foot slopes. In the turlough areas groundwater gleys and peat soils dominate due to the fluctuating groundwater. Based on the karst geology and connection to the surface through the exposed karst features, phosphorus would be considered the main nutrient at risk of loss. The main loss pathway is direct connection of the soil surface and runoff through the karst system to the groundwater.
Most of the farms in the catchment produce beef cattle and sheep at moderate stocking rates. There are a number of dairy farms which make up a significant area of the catchment and which are intensively farmed with high stocking rates and high inputs of nutrients from imported fertilisers and feedstuffs. The spring at Cregduff flows into the Bulkaun River, a tributary of the Robe which flows into Lough Mask just to the west of Ballinrobe.