A prototype framework for models of socio-hydrology: identification of key feedback loops and parameterisation approach

It is increasingly acknowledged that, in order to sustainably manage global freshwater resources, it is critical that we better understand the nature of human–hydrology interactions at the broader catchment system scale. Yet to date, a generic conceptual framework for building models of catchment systems that include adequate representation of socioeconomic systems – and the dynamic feedbacks between human and natural systems – has remained elusive. In an attempt to work towards such a model, this paper outlines a generic framework for models of socio-hydrology applicable to agricultural catchments, made up of six key components that combine to form the coupled system dynamics: namely, catchment hydrology, population, economics, environment, socioeconomic sensitivity and collective response. The conceptual framework posits two novel constructs: (i) a composite socioeconomic driving variable, termed the Community Sensitivity state variable, which seeks to capture the perceived level of threat to a community's quality of life, and acts as a key link tying together one of the fundamental feedback loops of the coupled system, and (ii) a Behavioural Response variable as the observable feedback mechanism, which reflects land and water management decisions relevant to the hydrological context. The framework makes a further contribution through the introduction of three macro-scale parameters that enable it to normalise for differences in climate, socioeconomic and political gradients across study sites. In this way, the framework provides for both macro-scale contextual parameters, which allow for comparative studies to be undertaken, and catchment-specific conditions, by way of tailored "closure relationships", in order to ensure that site-specific and application-specific contexts of socio-hydrologic problems can be accommodated. To demonstrate how such a framework would be applied, two socio-hydrological case studies, taken from the Australian experience, are presented and the parameterisation approach that would be taken in each case is discussed. Preliminary findings in the case studies lend support to the conceptual theories outlined in the framework. It is envisioned that the application of this framework across study sites and gradients will aid in developing our understanding of the fundamental interactions and feedbacks in such complex human–hydrology systems, and allow hydrologists to improve social–ecological systems modelling through better representation of human feedbacks on hydrological processes

Identification of the Major Hydrological Threats for Two Clay Pan Wetlands in the South West of Australia

Abstract: This study presents the findings of a wetland ecohydrological model (WET-0D), used to recreate a historical water regime and predict the future water regime for two clay pan wetlands in South West Western Australia. WET-0D simulates the major hydrological fluxes through three conceptual water storages including the open water/lake, and surrounding unsaturated and saturated zones. Groundwater -soil water balance -vegetation (GSV) dynamics are modelled with plant biomass simulated as three functional vegetation groups with differing water uptake strategies and dependence on water availability. The wetland model was driven by a simple catchment water balance model, using historical climate data from the Bureau of Meteorology (BoM). To simulate the potential impact of climate change on wetland ecohydrology, statistically downscaled output from a Global Climate Model (GCM), based on the IPCC SRES A2 scenario, was used to drive the models to predict potential future water regimes. This allowed us to gain an insight of the impact of projected drying climate on the clay pan ecosystems. Although both clay pan catchments experience very similar climates, differences in the partitioning of rainfall and subsequent flow generation, due to different vegetation, soil type and topography, results in dissimilar hydrological regimes. Differences in the hydrological regimes alter the way predicted climate change affects water flux and hydroperiod (period of surface flooding of a wetland) in both clay pan systems. Historically, the modelling predicts the lake level in the North East clay pan is more dependent on overland flow, while the South West clay pan is more dependent on shallow groundwater flow from a seasonal aquifer. Under a drying climate the modelling predicts, the South West clay pan will become increasingly overland flow dependent. However, the shallow groundwater inputs to the clay pan prolong inundation by reducing the rate of seepage from the clay pan. The partial clearing of the catchment area for the South West clay pan has maximised groundwater recharge efficiency allowing maintenance of ecological water requirements under a drying climate. The North East clay pan is under greater threat due to the reliance of surface water inflow and the lack of groundwater input due to differences in catchment characteristics

A General Lake Model (GLM 3.0) for linking with high-frequency sensor data from the Global Lake Ecological Observatory Network (GLEON)

The General Lake Model (GLM) is a one-dimensional open-source code designed to simulate the hydrodynamics of lakes, reservoirs, and wetlands. GLM was developed to support the science needs of the Global Lake Ecological Observatory Network (GLEON), a network of researchers using sensors to understand lake functioning and address questions about how lakes around the world respond to climate and land use change. The scale and diversity of lake types, locations, and sizes, and the expanding observational datasets created the need for a robust community model of lake dynamics with sufficient flexibility to accommodate a range of scientific and management questions relevant to the GLEON community. This paper summarizes the scientific basis and numerical implementation of the model algorithms, including details of sub-models that simulate surface heat exchange and ice cover dynamics, vertical mixing, and inflow–outflow dynamics. We demonstrate the suitability of the model for different lake types that vary substantially in their morphology, hydrology, and climatic conditions. GLM supports a dynamic coupling with biogeochemical and ecological modelling libraries for integrated simulations of water quality and ecosystem health, and options for integration with other environmental models are outlined. Finally, we discuss utilities for the analysis of model outputs and uncertainty assessments, model operation within a distributed cloud-computing environment, and as a tool to support the learning of network participants.</p

Exploring, exploiting and evolving diversity of aquatic ecosystem models: A community perspective

Here, we present a community perspective on how to explore, exploit and evolve the diversity in aquatic ecosystem models. These models play an important role in understanding the functioning of aquatic ecosystems, filling in observation gaps and developing effective strategies for water quality management. In this spirit, numerous models have been developed since the 1970s. We set off to explore model diversity by making an inventory among 42 aquatic ecosystem modellers, by categorizing the resulting set of models and by analysing them for diversity. We then focus on how to exploit model diversity by comparing and combining different aspects of existing models. Finally, we discuss how model diversity came about in the past and could evolve in the future. Throughout our study, we use analogies from biodiversity research to analyse and interpret model diversity. We recommend to make models publicly available through open-source policies, to standardize documentation and technical implementation of models, and to compare models through ensemble modelling and interdisciplinary approaches. We end with our perspective on how the field of aquatic ecosystem modelling might develop in the next 5–10 years. To strive for clarity and to improve readability for non-modellers, we include a glossary

Twenty-three unsolved problems in hydrology (UPH) – a community perspective

This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through on-line media, followed by two workshops through which a large number of potential science questions were collated, prioritised, and synthesised. In spite of the diversity of the participants (230 scientists in total), the process revealed much about community priorities and the state of our science: a preference for continuity in research questions rather than radical departures or redirections from past and current work. Questions remain focussed on process-based understanding of hydrological variability and causality at all space and time scales. Increased attention to environmental change drives a new emphasis on understanding how change propagates across interfaces within the hydrological system and across disciplinary boundaries. In particular, the expansion of the human footprint raises a new set of questions related to human interactions with nature and water cycle feedbacks in the context of complex water management problems. We hope that this reflection and synthesis of the 23 unsolved problems in hydrology will help guide research efforts for some years to come

Simulation tools for minimizing pathogen risk in drinking water reservoirs

Contamination of water supplies intended for human consumption by pathogenic microorganisms is a concern for water managers in developed and developing countries alike. Typically, pathogens are associated with disturbed landscapes such as those used for human settlements or agricultural practices, and they progress from the catchment to the river or stream during periods of significant rainfall. Ultimately, they reach drinking water reservoirs and are potentially distributed to consumers. There is therefore a need for tools that can be applied to assess pathogen fate and transport as they move through a reservoir. This paper documents the development of a suite of freely available tools that range in complexity from a simple web-based intrusion model (INFLOW), to a onedimensional hydrodynamic and pathogen model (DYRESM-CAEDYM), to a full three dimensional model of hydrodynamics and pathogen fate and transport (ELCOMCAEDYM). Results from the models are presented and assessed against data collected during a comprehensive field campaign in Australia that tracked pathogen concentrations throughout two reservoirs subjected to inflow forcing from rivers with high pathogen loads. All three models proved themselves as useful tools for investigating pathogen dynamics and are able to estimate dilution rates and timescales for risk reduction through inactivation and settling. The information provided by the models can be used to recommend a simple monitoring program and adaptive risk management strategies. The benefits and limitations of each of the models are also discussed.Matthew R. Hipsey, Jason P. Antenucci, Justin D. Brookes, Mike D. Burch and Rudi H. Regelhttp://www.cwr.uwa.edu.au/research/publications.php?rec=202

Hydrodynamic controls on oxygen dynamics in a riverine salt wedge estuary, the Yarra River estuary, Australia

Oxygen depletion in coastal and estuarine waters has been increasing rapidly around the globe over the past several decades, leading to decline in water quality and ecological health. In this study we apply a numerical model to understand how salt wedge dynamics, changes in river flow and temperature together control oxygen depletion in a micro-tidal riverine estuary, the Yarra River estuary, Australia. Coupled physical–biogeochemical models have been previously applied to study how hydrodynamics impact upon seasonal hypoxia; however, their application to relatively shallow, narrow riverine estuaries with highly transient patterns of river inputs and sporadic periods of oxygen depletion has remained challenging, largely due to difficulty in accurately simulating salt wedge dynamics in morphologically complex areas. In this study we overcome this issue through application of a flexible mesh 3-D hydrodynamic–biogeochemical model in order to predict the extent of salt wedge intrusion and consequent patterns of oxygen depletion. The extent of the salt wedge responded quickly to the sporadic riverine flows, with the strength of stratification and vertical density gradients heavily influenced by morphological features corresponding to shallow points in regions of tight curvature ("horseshoe" bends). The spatiotemporal patterns of stratification led to the emergence of two "hot spots" of anoxia, the first downstream of a shallow region of tight curvature and the second downstream of a sill. Whilst these areas corresponded to regions of intense stratification, it was found that antecedent conditions related to the placement of the salt wedge played a major role in the recovery of anoxic regions following episodic high flow events. Furthermore, whilst a threshold salt wedge intrusion was a requirement for oxygen depletion, analysis of the results allowed us to quantify the effect of temperature in determining the overall severity and extent of hypoxia and anoxia. Climate warming scenarios highlighted that oxygen depletion is likely to be exacerbated through changes in flow regimes and warming temperatures; however, the increasing risk of hypoxia and anoxia can be mitigated through management of minimum flow allocations and targeted reductions in organic matter loading. A simple statistical model (R2 > 0.65) is suggested to relate riverine flow and temperature to the extent of estuary-wide anoxia

A three dimensional model for Cryptosporidium dynamics in lakes and reservoirs

A model of Cryptosporidium oocyst dynamics for lakes and reservoirs is presented. The model consists of a module that simulates oocyst inactivation, resuspension, settling and aggregation onto particles. This module was coupled to the three-dimensional Estuary Lake and Coastal Ocean Model (ELCOM), which was used to simulate lake hydrodynamics in addition to oocyst advection and turbulent diffusion. A field experiment that tracked the passage of a flood inflow throughout Myponga Reservoir, South Australia, was used to validate the coupled model. The model accurately captured the thermal dynamics, and the spatial and temporal distribution of different inorganic particle size classes and oocysts. The model and data indicate that oocysts do not readily attach to inorganic particles as other researchers have suggested but settle as free-floating oocysts according to Stoke’s sedimentation dynamics. The reduction in oocysts between the inflow and the offtake due to settling is therefore not as significant as previously thought. The potential for inactivation was also found to be small relative to the timescales for transport. The model is a useful tool to examine oocyst dynamics in lakes and reservoirs, to consider risk management assessments of different scenarios, and to assess the effectiveness of different sampling strategies.Matthew R. Hipsey, Jason P. Antenucci, Justin D. Brookes, Michael D. Burch, Rudi H. Regel and Leon Lindenhttp://www.jrbm.net/pages