Revisiting the challenges posed by V Klemeš (1993) to reassess hydrological methodology in the Humid Tropics Some implications for water resource assessment Mike Lee Principal Environmental Consultant GHD
This presentation The late V Klemeš was a commanding figure in modern hydrology. His landmark paper The Problems of the Humid Tropics – Opportunities for Reassessment of Hydrological Methodology appeared in 1993 The paper points to the profound challenges in applying many aspects of conventional hydrological methodology, mostly developed in temperate regions and based on assumptions of stationarity, to the humid tropics This presentation revisits the paper and draws out some practical implications for water resource assessment and management. This presentation provides a personal perspective and does not purport to present the views of the presenter’s home organisation.
Vit Klemeš
The Problems of the Humid Tropics - Opportunities for Reassessment of Hydrological Methodology , V Klemeš Hydrology and Water Management in the Humid Tropics International Hydrology Series, UNESCO and University of Cambridge Press, 1993 Key messages � The hydrology of the humid tropics is very different from temperate regions where most methodology has been developed � Nonstationarity is a bigger issue � past records tell us less about the future � Macro-hydrological processes are more important � atmosphere-ocean-land interactions are strong drivers � Eco-hydrology is more important � soil-vegetation-atmosphere processes are more dominant � There are profound implications for water resources assessment and management
Nonstationarity “the shrinkage of the time scale on which nonstationarity is becoming significant is presently largest in the humid tropics. The changes induced there by "modern" causes (CO2 concentrations and the long-range transport of pollutants) are happening at the same time as the drastic land-use changes. Such changes were spread over several centuries in most of the temperate zones.” Klemeš (1993)
Nonstationarity(?) Source : National Agriculture and Climate Change Action Plan, 2008 http://www.managingclimate.gov.au/wp- content/uploads/2010/12/3-WA_Climate- Change-observed-changes_FINAL.pdf
Nonstationarity(?) Inflows to Sydney's Hawkesbury-Nepean dams (excluding Shoalhaven transfers ) Source: Sydney Water http://www.sydneywater.com.au/Publications/Reports/AnnualReport/2007/menu/performance/goal1/desalination.cfm
Desalination as ‘Insurance’ Major Australian Desalination Plants Plant Average Number of Cost Planned Completion production people (AUD) wind farms Ml/day whose for offsets water needs MW are met Perth (Kwinana) 144 0.3m $387m 80 2006 Tugun (SE 125 $1.2bn 2009 Queensland) Sydney (Kurnell) 250 0.7m $1.9bn 140 2010 Adelaide (Port 270 0.6m $1.8bn 2012 Stanvac) Melbourne 400 1.3m $4bn 120 2012 (Wonthagi) All reverse osmosis World-wide commissioned capacity (sea water and brackish) reported as 53000 Ml/day (WDR, 2009) Various public sources
Nonstationarity (?) Raff, 2010 Moving window Expanding retrospective view
Nonstationarity Flood frequency based on climate predictions , D. Raff, Proceedings of Workshop on Nonstationarity, Hydrologic Frequency Analysis and Water Management , January 2010 Boulder, Colorado http://www.cwi.colostate.edu/publications/is/109.pdf
Designing for (Safe) Exceedance P e = 1 – [1-(1/T)] n T n P e ‘100 year 30 26.0% event’ 50 39.5% ‘500 year 30 5.8% event’ 50 9.5% ‘10 000 30 0.3% year event’ 50 0.5% T Return Period N number of years P e Probability of event being exceeded over the period Gillespie et al, 2002 http://www.bewsher.com.au/pdf/EMA_1.pdf Probability of scoring 11 with one throw of 2 six-sided dice = 5.6%
Nonstationarity “Many sound water management decisions can be made with surprisingly little hydrological information. The lack of knowledge can be compensated for by a corresponding increase in the robustness and resilience of the design of the relevant facilities and by maintaining flexibility of future options.” “In all but the simplest technological decisions, the concept of optimization is invalid because its underlying assumptions, including social, political, economic and other conditions, are changing rapidly and usually unpredictably.” “It is safe to say that most water management projects, however thoroughly their design may have been optimized, were far from optimal by the time they were put into operation.” “The return to conservative decisions with high safety margins and ample flexibility is particularly called for in the environmental context, and in regions such as the humid tropics which are undergoing rapid change.” Klemeš (1993)
Macro-hydrology “In the humid tropics, the overall control of hydrological processes by the global atmospheric and ocean circulation is more direct than in other regions - - ” “The dynamic features originating in the tropics operate on large spatial scales and on a wide spectrum of time - -” “This stresses the need for analyzing the hydrological conditions and their changes in a broad atmosphere ocean-land context. Such an approach also forces an explicit recognition of the fact that the key to understanding hydrological phenomena lies outside hydrology, certainly outside the domain of the classical hydrology - in the narrow sense of the word.” Klemeš (1993)
Macro-hydrology “macro-hydrological analyses will not be feasible without a qualitatively different database than the one provided by the classical networks of sparse point measurements which hinge on local accessibility and availability of qualified personnel. The new database will have to comprise "hydrological fields", i.e., time series of areal distributions of various hydrological and related variables. Such a database is only now coming within reach through the newest remote sensing and data transmission technologies.” Klemeš (1993)
Eco-hydrology “Given the importance of vegetation in the hydrology of humid tropics and the rate and volume of their present deforestation, a thorough scientific understanding of the quantitative relationships within the soil- vegetation-atmosphere segment of the hydrological cycle is indispensable for sound hydrological assessment and prediction” “ This understanding also is needed for an adequate parameterization of the land surface processes in the GCMs in order to make it possible to model the present dynamics of the water and energy fluxes in the humid tropics” “quantitative eco-hydrology is the key to tackling - - (a) the local hydrological effects of local environmental changes, (b) the external effects of the local environmental changes and (c) the local effects of external environmental changes such as global warming, the long range transport of chemical pollutants and aerosols, etc” Klemeš (1993)
Macro-hydrology, Eco-hydrology and Water Resource Assessment � A key aim of water resource assessments is to provide estimates of water availability over a given period of time � A water balance framework aims to provide a conceptual basis through which fluxes/ storages can be estimated for the purpose of water resource assessments � Inputs - Outputs – Change in storage = error term � Water availability to meet growing demands � Water balances help identify the consequences on surface water and groundwater stores of increased water extractions, and inter-basin transfers
Water Resource Assessment Regional water balance framework - Australian Water Resource Assessments System http://www.bom.gov.au/water/about/publications/document/Review_of_Methods.pdf
Water Resource Assessment Australian Water Resource Assessments System Continental water balance On-ground data sparse in many areas Model-data fusion •on-ground data •satellite, radar •biophysical models http://www.clw.csiro.au/publications/waterforahealthycountry/2010/wfhc- WIRADA-factsheet-catchment-continent.pdf
Australian Water Resource Assessment System AWRA landscape Model - CSIRO / Bureau of Meteorology ‘macro-hydrology’ ‘eco-hydrology’ ‘eco-hydrology’ http://www.clw.csiro.au/publications/waterforahealthycountry/2010/wfhc-aus-water-resources-assessment-system.pdf
Australian Water Resource Assessment System AWRA Landscape Model testing - CSIRO / Bureau of Meteorology Monthly mean streamflows “Overall it is concluded that even without local catchment calibration the AWRA model provides useful estimates of catchment streamflow. Important characteristics are the apparent lack of bias and the strongly improved performance at longer time scales and larger spatial scales. On the basis of these findings, it is recommended that that the results can already be used for water accounting and assessment purposes as is.” http://www.clw.csiro.au/publications/waterforahealthycountry/2010/wfhc-awras-evaluation-against-observations.pdf
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