Ian Cartwright

• PhD
• Professor at Monash University (Australia)

Estimating groundwater recharge rates is important to understand and manage groundwater. Numerous studies have used collated recharge datasets to understand and project regional- or global-scale groundwater recharge rates. However, recharge estimation methods all have distinct assumptions, quantify different recharge components and operate over dif...

Developing conceptual models is a critical step in hydrogeological studies that should utilise multiple lines of evidence and data types to minimise conceptual uncertainty, particularly in data-sparse systems. This study used new and existing major ion and isotope (O, H, Sr, C) data sets to refine a previous hydraulic-head-based conceptual model of...

Estimating groundwater recharge rates is important to understand and manage groundwater. Numerous studies have used collated recharge datasets to understand and project regional or global-scale recharge rates. Recharge estimation methods each have distinct assumptions, quantify different recharge components, and operate over different temporal scal...

Land use affects evapotranspiration rates and is a primary driver of the catchment water balance. The water balance of two catchments in southeastern Australia dominated by either grazed pasture or blue gum (Eucalyptus globulus) plantation was studied, focusing on the patterns of evapotranspiration (ET) throughout the year. Rainfall, streamflow, an...

The Millennium Drought lasted more than a decade and is notable for causing persistent shifts in the relationship between rainfall and runoff in many southeastern Australian catchments. Research to date has successfully characterised where and when shifts occurred and explored relationships with potential drivers, but a convincing physical explanat...

Study region Australia Study focus Our incomplete knowledge of groundwater systems and processes imposes barriers in attempting to manage groundwater sustainably. Challenges also arise through complex institutional arrangements and decision-making processes, and the difficulty in involving stakeholders. In some areas, these difficulties have led t...

Sustainable management of estuaries depends on understanding the synergistic effects of nutrients and hydrological factors on estuarine food webs. We examined how phytoplankton, zooplankton and selected fish larval counts (Acanthopagrus butcheri, black bream) vary in relation to groundwater inputs and environmental flow releases (EFRs) in a small,...

Determining the mean transit times (MTTs) and water sources in catchments at different flow conditions helps better understand river functioning, and manage river health and water resources. Despite being common in a range of environments, the MTTs and water sources in intermittent streams are much less well understood compared to perennial streams...

Land use affects evapotranspiration rates and is a primary driver of the catchment water balance. The water balance of two catchments in southeastern Australia dominated by either grazed pasture or blue gum ( Eucalyptus globulus ) plantation was studied, focusing on the patterns of evapotranspiration (ET) throughout the year. Rainfall, streamflow,...

The establishment and expansion of commercial plantations for timber production and carbon sequestration raises concerns because of their large water use. Eucalyptus globulus (blue gum) is one of the most planted species globally, as it grows rapidly and is adaptable to a range of climatic conditions. The dearth of experimental observations on wate...

The Millennium Drought lasted more than a decade, and is notable for causing persistent shifts in the relationship between rainfall and runoff in many south-east Australian catchments. Research to date has successfully characterised where and when shifts occurred and explored relationships with potential drivers, but a convincing physical explanati...

Streams may be connected to a large store of water, such as regional groundwater, and/or sustained by smaller near-river stores (such as riparian groundwater). Documenting the sources of water in streams is important for understanding catchment water balances, protecting riverine environments from pollution, and predicting the efforts of near-river...

Determining the mean transit times (MTTs) and water sources in catchments at different flow conditions helps better understand river functioning, manage riverine system health and water resources, and discern the responses to climate change and global water stress. Despite being common in a range of environments, understanding of MTTs and variable...

Baseflow to rivers comprises regional groundwater and lower-salinity intermediate water stores such as interflow, soil water, and bank return flows. Chemical mass balance (CMB) calculations based on the specific conductivity (SC) of rivers potentially estimate the groundwater contribution to baseflow. This study discusses the application of the CMB...

Bedding-parallel fibrous calcite veins crop out at two Permian carbonate localities in the Phetchabun area, central Thailand, within the Nam Duk and Khao Khwang Formations. Samples are studied to determine their petrographic, geochemical and isotopic character, depositional and diagenetic associations and controls on the formation of fibrous calcit...

Determining the sources and mean transit times (MTTs) of water that generates streamflows is important for understanding and managing headwater catchments. The sources and especially the MTTs of water that contributes to streamflow in seasonally intermittent streams are far less studied than for perennial streams. Here we use major ions, dissolved...

The chloride mass balance (CMB) method is widely used to estimate long-term rates of groundwater recharge. In regions where surface water runoff is negligible, recharge can be estimated using measurements of chloride concentrations of groundwater and precipitation, and an estimate of long-term average rainfall. This paper presents the Chloride Mass...

The combined use of deuterium and tritium to determine travel time distributions (TTDs) in streams is an important development in catchment hydrology (Rodriguez et al., 2021). This comment takes issue with Rodriguez et al.'s assertion that the truncation hypothesis may not hold for catchments in general, i.e. that the use of stable isotopes alone m...

Carbon-14 (14C) is routinely used to determine mean residence times (MRTs) of groundwater. 14C-based MRT calculations typically assume that the unsaturated zone is in equilibrium with the atmosphere, controlling the input 14C activity. However, multiple studies have shown that unsaturated zone 14C activities are lower than atmospheric values. Despi...

Baseflow to rivers comprises regional groundwater and lower salinity intermediate water stores such as interflow, soil water, and bank return flows. Chemical mass balance (CMB) calculations based on the specific conductivity (SC) of rivers potentially estimates the groundwater contribution to baseflow. This study discusses the application of the CM...

The identification of nitrogen sources and cycling processes is critical to the management of nitrogen pollution. Here, we used both stable (δ15N-NO3-, δ18O-NO3-, δ15N-NH4+) and radiogenic (222Rn) isotopes together with nitrogen concentrations to evaluate the relative importance of point (i.e. sewage) and diffuse sources (i.e. agricultural-derived...

In this study, the non-stationarity of total annual extreme rainfall was analysed to acquire the accountable physical phenomena and SPI was estimated to assess the extent of drought in the Banas River basin. In the Banas basin, to manage water demands during dry days, artificial groundwater recharge structures are built. Based on the non-stationary...

Documenting the distribution, sources, and fluxes of baseflow discharge into rivers is important for their management and for maintaining ecosystem health. This study uses major ion geochemistry, 222Rn, and 3H to differentiate between the input of low-salinity near-river waters (bank storage and return waters and/or interflow) and regional groundwa...

Carbon-14 (14C) is routinely used to determine mean residence times (MRTs) of groundwater. 14C-based MRT calculations typically assume that the unsaturated zone is in equilibrium with the atmosphere, controlling the input 14C activity. However, multiple studies have shown that unsaturated zone 14C activities are lower than atmospheric values. Despi...

The combined use of deuterium and tritium to determine travel time distributions (TTDs) in streams is an important development in catchment hydrology (Rodriguez et al, 2021). This comment takes issue with Rodriguez et al.'s general rejection of the truncation hypothesis, i.e. that the almost exclusive use of stable isotopes has truncated our vision...

Estuaries have been identified as sources of nitrous oxide (N2O) emissions to the atmosphere but questions remain as to which production pathway(s) govern the oversaturation of N2O observed in most estuaries worldwide. Here, we use a suite of nitrate and N2O isotopes, as well as the 15N site preference signatures of N2O to assess (1) the relative i...

Understanding the applicability and uncertainties of methods for documenting recharge rates in semi-arid areas is important for assessing the successive effects of land-use changes and understanding groundwater systems. This study focuses on estimating groundwater recharge rates and understanding the impacts of land-use changes on recharge rates in...

Specific conductivity (SC) is commonly used to estimate the proportion of baseflow (i.e., waters from within catchments such as groundwater, interflow, or bank return flows) contributing to rivers. Reach-scale SC comparisons are also useful for identifying where multiple water stores contribute to baseflow. Daily SC values of adjacent gauges in Aus...

Determining recharge rates is critical for understanding and managing groundwater systems. This study compares recharge rates estimated using different methods in a temperate catchment (the Ovens Valley, southeast Australia). A catchment water balance yields recharge rates of 110–410 mm yr⁻¹, with the range reflecting uncertainties in evapotranspir...

Determining mean transit times in headwater catchments is critical for understanding catchment functioning and understanding their responses to changes in landuse or climate. Determining whether mean transit times (MTTs) correlate with drainage density, slope angle, area, or land cover permits a better understanding of the controls on water flow th...

The temporary storage of river water in riverbanks and its subsequent return to the river is an important part of the hydrological cycle. Detailed multi-year head and electrical conductivity (EC) variations document the spatial and temporal scales of bank infiltration and return flows in the Ovens catchment, southeast Australia. The study represent...

Documenting the processes that control the geochemistry of rivers at different streamflows is important for understanding catchment processes and calculating solute fluxes. The concentrations of most major ions (Na, Ca, K, Mg, HCO3, Cl, and SO4) in southeast Australia rivers vary little with streamflow and can be defined as being chemostatic or che...

Intermittent headwater catchments constitute a significant proportion of many stream networks. In semi-arid climates, intermittent headwater streams flow only following periods of sustained rainfall. There is commonly a rapid response of streamflow to rainfall; however, whether this is the input of recent rainfall or displacement of water stored in...

Understanding recharge in semi-arid areas is important for the sustainable management of groundwater resources. This study focuses on estimating groundwater recharge rates and understanding the impacts of land-use changes on recharge in a semi-arid area. Two adjacent catchments in southeast Australia were cleared ~180 years ago following European s...

Groundwater is a pivotal resource for many human populations and ecosystems. However, in groundwater sciences (hydrogeology), there remain many challenges in understanding key processes; including groundwater origins, water fluxes, and controls on water quality. The stable isotopes of water are naturally occurring, form part of the water molecule,...

Fresh groundwater on barrier islands is affected by changing sea levels and precipitation variability due to climate change and is also vulnerable to anthropogenic processes, such as contamination and groundwater over-abstraction. Constraining groundwater mean residence times (MRTs) and flow paths is essential for understanding and managing these r...

Archives of past climates and environments are essential for understanding Earth history and provide a baseline for studying the impacts of anthropogenic climate change. Because groundwater in large basins typically has residence times of thousands to tens-of-thousands of years, it potentially records changes to the hydrosphere over the transition...

Documenting the processes that control the variations in stream geochemistry at different streamflows is important for being able to use chemical tracers to understand catchment functioning. The concentrations of most solutes, including reactive cations (e.g., Na, Ca, K, and Mg) and anions that are primarily derived from precipitation (Cl and Br),...

Choosing appropriate recharge methods is important for understanding how groundwater recharge is impacted by successive land-use changes in semi-arid areas. This study examines two contrasting catchments in western Victoria, Australia, that were cleared following European settlement ~180 years ago, one of which was subsequently replanted with plant...

Groundwater is an important resource in arid and semi-arid regions and determining its residence times is critical for sustainable use. Radiocarbon (¹⁴C) is currently the primary geochemical tracer for determining residence times of regional groundwater systems. The analysis of ¹⁴C contents of dissolved inorganic carbon (DIC) became more straightfo...

Fresh groundwater on barrier islands is affected by changing sea levels, groundwater use and precipitation variability due to climate change. These systems are also vulnerable to contamination and groundwater over-abstraction. Constraining groundwater mean residence times (MRT) and flow paths are essential for understanding and managing these resou...

Floodplains may alternate between discharge zones for regional groundwater and areas of recharge from river water during high-flow events. Understanding the mechanisms and timescales of recharge on floodplains is important for their management and for the protection of fragile ecosystems. The floodplains of the River Murray host important ecosystem...

Transient storage zones (TSZs) are located at the interface of rivers and their abutting aquifers and play an important role in hydrological and biogeochemical functioning of rivers. The natural radioactive tracer 222 Rn is a particularly well-suited tracer for studying TSZ water exchange and age. Although 222 Rn measurement techniques have develop...

Documenting the sources and residence times of water that contributes to streamflow is important for understanding processes in river catchments. The residence times of bank storage and return flow and its influence on river water chemistry in the upper Barwon River of southeast Australia were investigated using stable (¹⁸O, ²H, and ¹³C) and radioa...

Understanding the sources and transit times of water that generates streamflow in headwater streams is important for understanding catchment functioning. This study determines the water sources and transit times in first-order streams from a temperate rainforest in the Otway Ranges, southeast Australia. Comparison of the major ion geochemistry of s...

Documenting the changing sources of water during high streamflows following rainfall is important for understanding catchment behaviour. This study uses tritium (3H), major ion concentrations, and δ18O values to identify the sources of water that sustain streamflow in the upper Yarra and Latrobe catchments of southeast Australia over two high flow...

Headwater catchments provide substantial streamflow to rivers even during long periods of drought. Documenting the mean transit times (MTT) of stream water in headwater catchments and therefore the retention capacities of these catchments is crucial for water management. This study uses time series of ³H activities in combination with major ion con...

Understanding the timescales of water flow through catchments and the origins of stream water at different flow conditions is critical for understanding catchment behaviour and managing water resources. Here, tritium (3H) activities, major ion geochemistry and discharge data were used in conjunction with Lumped Parameter Models (LPMs) to investigat...

Catchments draining upland peat in the Victorian Alps, Australia contain water that has ³H activities closely similar to modern rainfall implying very short transit times (<2 years). By contrast the water that drains adjacent eucalypt forest has mean transit times of several years to decades. The differences in transit times most likely reflect the...

Estimating the time required for water to travel through headwater catchments from where it recharges to where it discharges into streams (the transit time) is important for understanding catchment behaviour. This study uses tritium (³H) activities of stream water to estimate the mean transit times of water in the upper Latrobe and Yarra catchments...

Documenting the location and magnitude of groundwater recharge is critical for understanding groundwater flow systems. Radioactive tracers, notably ¹⁴C, ³H, ³⁶Cl, and the noble gases, together with other tracers whose concentrations vary over time, such as the chlorofluorocarbons or sulfur hexafluoride, are commonly used to estimate recharge rates....

Freshwater lenses are lenticular bodies of fresh (TDS < 1000 mg/L) groundwater that develop above more saline groundwater within the same host aquifer due in part to buoyancy. In contrast to the widely studied situation of freshwater lenses in coastal aquifers, the formation, location and persistence of freshwater lenses in terrestrial settings are...

Documenting the origins, residence times, and movement of groundwater and the solutes that it contains is critical to understanding hydrogeological systems. This study uses Cl mass balance to determine the Cl accession time (i.e. the time required for Cl to accumulate) and ³⁶Cl to estimate the residence times of Cl in the Victorian portion of the M...

It has been widely acknowledged that environmental literacy can provide a strong foundation for future environmental responsiveness, as well as help in the transition towards more sustainable societies and healthy living. According to environmentalists and social scientists, behavioural intentions to sustainable consumption and lifestyle among citi...

The residence times of groundwater and chloride and the processes contributing to the development of saline (total dissolved solids (TDS) up to 45,379 mg/L) groundwater within the Barwon River Catchment of southeast Australia were investigated using major ion, stable isotope (δ¹⁸O, δ²H, and δ¹³C) and radioactive isotope (³H, ¹⁴C, ³⁶Cl) geochemistry...

Analytical solutions that use diurnal temperature signals to estimate vertical fluxes between groundwater and surface water based on either amplitude ratios (Ar) or phase shifts (Δϕ) produce results that rarely agree. Analytical solutions that simultaneously utilize Ar and Δϕ within a single solution have more recently been derived, decreasing unce...

Heat is a powerful tracer to quantify fluid exchange between surface water and groundwater. Temperature time series can be used to estimate pore water fluid flux, and techniques can be employed to extend these estimates to produce detailed plan-view flux maps. Key advantages of heat tracing include cost-effective sensors and ease of data collection...

Peatlands are a distinctive and important component of many upland regions that commonly contain distinctive flora and fauna which are different from those of adjacent forests and grasslands. Peatlands also represent a significant long-term store of organic carbon. While their environmental importance has long since been recognised, water transit t...

Documenting the interaction between groundwater and rivers is fundamental to understanding hydrological systems. While many studies have examined the location and magnitude of groundwater inflows to rivers, much less is known about the transit times of water in catchments and from where in the aquifer the groundwater originates. Resolving those que...

Documenting the interaction between groundwater and rivers is fundamental to understanding hydrological systems. While many studies have examined the location and magnitude of groundwater inflows to rivers, much less is known about the transit times of water in catchments and from where in the aquifer the groundwater originates. Resolving those que...

Obtaining reliable estimates of vertical groundwater flows remains a challenge but is of critical importance to the management of groundwater resources. When large scale land clearing or groundwater extraction occurs, methods based on water table fluctuations or water chemistry are unreliable. As an alternative, a number of methods based on tempera...

Understanding the location and magnitude of groundwater inflows to rivers is important for the protection of riverine ecosystems and the management of connected groundwater and surface water systems. This study utilizes 222Rn activities and Cl concentrations in the Avon River, southeast Australia, to determine the distribution of groundwater inflow...

Peatlands are a distinctive and important component of many upland regions that commonly contain distinctive flora and fauna that are different from adjacent forests and grasslands. Peatlands also represent a significant long-term store of organic carbon. While their environmental importance has long since been recognised, water transit times withi...

Stable isotopic studies, focused on calcite cement, vein-fill calcite, various bioclasts and early burial diagenetic cement rims and replacements, can be used to define the burial evolution of ancient carbonates in outcrop in central Thailand and the resulting curve applied to better understand the timing and positions of subsurface poro-perm evolu...

Temperature is a powerful tracer to estimate vertical flows in the hyporheic zone. Temperature time series can be used to obtain estimates of fluid flux, and techniques can be employed to extend these estimates into plan-view flux maps. Key advantages of the use of heat as a tracer include that sensors are inexpensive, and that data can be collecte...

Steady state 1D analytical solutions to estimate groundwater fluxes from temperature profiles are an attractive option because they are simple to apply, with no complex boundary or initial conditions. Steady state solutions have been applied to estimate both aquifer scale fluxes as well as to estimate groundwater discharge to streams. This study ex...

Obtaining estimates of vertical groundwater flows remains a challenge in hydrogeology. A number of methods based on temperature-depth ( T-z) profiles are available to provide vertical groundwater flow estimates. However, methods based on steady state assumptions have been shown to be inappropriate for sites that have experienced land surface warmin...

The Procedia Paper is a conference abstract. The full paper is published in HESS and may be downloaded here Headwater streams in the Ovens catchment, southeast Australia, have 3H activities between 1.63 and 2.45 TU that are lower than those of local rainfall (∼3 TU). The variation of 3H activities and major ion concentrations with streamflow impli...

Understanding the location and magnitude of groundwater inflows to rivers is important for the protection of riverine ecosystems and the management of connected groundwater and surface water systems. Downstream trends in 222Rn activities and Cl concentrations in the Avon River, southeast Australia, implies that it contains alternating gaining and l...

The dynamic response of groundwater discharge to external influences such as rainfall is an often neglected part of water and solute balances in wetlands. Here we develop a new field platform for long-term continuous 222Rn and electrical conductivity (EC) measurements at Sale Wetland, Australia to study the response of groundwater discharge to stor...

Headwater streams contribute a significant proportion of the total flow to many river systems, especially during summer low-flow periods. However, despite their importance, the time taken for water to travel through headwater catchments and into the streams (the transit time) is poorly understood. Here, 3H activities of stream water are used to def...

Headwater streams contribute a significant proportion of the total flow to many river systems, especially during summer low-flow periods. However, despite their importance, the time taken for water to travel through headwater catchments and into the streams (the transit time) is poorly constrained. Here, 3H activities of stream water are used to de...

Surface water sampling of 222-Rn is often used to map zones of groundwater discharge. Sampling of groundwater 222-Rn is less often used to estimate water residence times in shallow alluvial systems. Radon groundwater grab samples offer a discrete time snapshot of flow path integrated Rn activities. During a pumping experiment on the banks of Maules...

Understanding groundwater-surface water exchange in river banks is crucial for effective water management and a range of scientific disciplines. While there has been much research on bank storage, many studies assume idealised aquifer systems. This paper presents a field-based study of the Tambo Catchment (southeast Australia) where the Tambo River...

Nitrate (NO3−) contamination in groundwater is a worldwide phenomenon and a pervasive environmental problem, particularly when NO3−-enriched groundwater discharges into a nitrogen-limited estuarine environment through submarine groundwater discharge (SGD). SGD is often associated with eutrophication which ultimately alters the coastal ecology of th...

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 222Rn. Durin...

Understanding the behaviour and variability of environmental tracers is important for their use in estimating groundwater discharge to rivers. This study utilizes a multi-tracer approach to quantify groundwater discharge into a 27 km upland reach of the Gellibrand River in southwest Victoria, Australia. Ten sampling campaigns were conducted between...

Knowledge of groundwater residence times and recharge locations is vital to the sustainable management of groundwater resources. Here we investigate groundwater residence times and patterns of recharge in the Gellibrand Valley, southeast Australia, where outcropping aquifer sediments of the Eastern View Formation form an "aquifer window" that may r...

Carbon (C) and alkalinity export from two adjacent intertidal inlets with different terrestrial inputs was investigated. One inlet receives a small creek from an agriculturally dominated catchment, leading to the input of terrestrially sourced material, whereas the other is relatively isolated from terrestrial inputs. Using time-series measurements...

We used d 15 N-nitrate (NO { 3) and d 18 O-NO { 3 to unravel the provenance and fate of NO { 3 in a groundwater-fed estuary. A total of 13 monthly and two time series surveys were undertaken in the Werribee River estuary near Melbourne, Australia. The different survey timescales provided a comprehensive evaluation of the hydrological effects on the...

A stable isotopic study, focused on calcite cements, vein-fill calcite and various bioclasts was conducted on variably deformed and thrusted Lower and Middle Permian carbonates of the Saraburi Group. Samples were collected in quarry faces across 3 areas in the Saraburi-Lopburi region of central Thailand. Stable isotope crossplots (carbon and oxygen...