Mapping and quantifying groundwater inflows to Deep Creek (Maribyrnong catchment, SE Australia) using 222Rn, implications for protecting groundwater-dependant ecosystems. (January 2015)

• Record Type: Journal Article
• Authors: Cartwright, Ian; Gilfedder, Benjamin
• Is Part Of: Applied geochemistry. Volume 52(2015:Jan.)
• Page Start: 118
• Page End: 129
• Publication Date: 2015-01
• Subjects: Environmental geochemistry -- Periodicals; Water chemistry -- Periodicals; Geochemistry -- Social aspects -- Periodicals; Geochemistry -- Periodicals; 551.9
• DOI: 10.1016/j.apgeochem.2014.11.020
• Languages: English
• ISSNs: 0883-2927

Abstract

Highlights: Groundwater inflows in a chain-of-ponds river quantified. Groundwater inflow vs. discharge relationship determined using Rn. First long-term continuous Rn monitoring in a river indicates temporal changes to groundwater inflows. Application to protection of groundwater-dependant ecosystems. Abstract: Understanding groundwater inflows to rivers is important in managing connected groundwater and surface water systems and for protecting groundwater-dependant ecosystems. This study defines the distribution of gaining reaches and estimates groundwater inflows to a 62 km long section of Deep Creek (Maribyrnong catchment, Australia) using 222 Rn. During summer months, Deep Creek ceases to flow and comprises a chain of ponds that δ 18 O and δ 2 H values, major ion concentrations, and 222 Rn activities imply are groundwater fed. During the period where the river flows, the relative contribution of groundwater inflows to total river discharge ranges from ∼14% at high flow conditions to ∼100% at low flows. That the predicted groundwater inflows account for all of the increase in discharge at low flow conditions lends confidence to the mass balance calculations. Near-continuous 27 week 222 Rn monitoring at one location in the middle of the catchment confirms the inverse correlation between river discharge and relative groundwater inflows, and also implies that there are limited bank return flows. Variations in groundwater inflows are related to geology and topography. High groundwater inflows occur where the river is at the edge of its floodplain, adjacent to hills composed of basement rocks, or flowing through steep incised valleys. Understanding the distribution of groundwater inflows and quantifying the contribution of groundwater to Deep Creek is important for managing and protecting the surface water resources, which support the endangered Yarra pygmy perch.