Lambert Allan O

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Allan Lambert


Allan Oswald Lambert 1940 (Liverpool) -


Allan Lambert was born in Liverpool and graduated from Liverpool University 1st Class Honours B.Eng in Civil Engineering in 1961 and M.Eng by dissertation in open channel Hydraulics for the Mersey River Board where he became interested in hydrology, achieving a Diploma in Hydrology with Distinction at the University of Newcastle upon Tyne in 1964.

In 1965 he was appointed Hydrologist at Usk River Authority and joined British Hydrological Society and the Institution of Water Engineers. As hydrologist, then Water Resources Engineer at Dee & Clwyd River Authority in 1966, his activities included implementation of abstraction licencing and Hydrometric Schemes, strategic management of the multipurpose River Dee Regulation, liaison with the Water Resources Board for the River Dee Research Programme, and fluvial and tidal flood forecasting and warning schemes.

In 1974, after a spell at Manager of Research and Data Collection at Northumbrian Water Authority, he returned to Welsh Water Authority as a Management Team member of Dee and Clwyd River Division, chairing the Statutory River Dee Consultative Committee, and managing the development and testing of the 25 Ml/d River Clwyd Augmentation and Abstraction Scheme from groundwater.

Allan became a Chartered Civil Engineer in 1974, a member of the UK Water Industry Delegation to Russia/Ukraine 1974, the UK Delegation to the Commission for Hydrology and the NERC Science Management Audit of Institute of Hydrology in 1984, and a Fellow of the Chartered Institution of Water Engineers and Scientists in 1987.

As a BHS Main Committee member since 1987, then President in 1989-91, he promoted BHS as a welcoming society for younger members and arranged access to BHS funds (previously held by the Royal Society) to assist them to attend the Peter Wolf Young Hydrologist Career Events. Allan also introduced President-Elects into the BHS Management Committee structure and wrote the first BHS Occasional Paper on Control Rules for Water Supply Systems. Allan retired from the Water Loss Research and Analysis (WLR&A) Ltd Consultancy in 2021.

Hydrological Achievements[edit]

The ISO Forecasting Model[edit]

In real-time forecasting of floods in smallish catchments where river channels are relatively steep, with little in the way of soil/ground water storage, river channel or flood plain storage, the flood moves downstream mainly by translation with a time lag between points A and B. For larger flood events to occur, the soil needs to become near-saturated, so the concept of treating the soil as a leaky bucket with holes at various heights, rather like the classical storage component based on Bernoulli’s equation. As the rain (inflow to the bucket) commences, the bucket starts to fill, and starts to flow out of the lowest hole in the side. If the inflow rate (mm/hour) is more than the outflow rate (mm/hour), the storage in the bucket will continue to rise, and the outflow rate will rise as a consequence (more holes come into play with a larger head of water). Thus, in the simplest possible scenario:

  • if the inflow rate to the bucket (or catchment area) exceeds the outflow rate, the storage and the outflow will continue to rise (rising limb of flood hydrograph)
  • when the inflow rate equals the outflow rate, the flood flow rate with level out (peak), and
  • as the inflow rate (rainfall mm/hr) reduces, the storage and the outflow rate will diminish (recession)

The model adds a component to assess the translation time from the ‘model’ situated in the middle of the catchment to the point on the river where forecasts are required to establish whether the river will continue to rise, level out, then begin to fall.

Allan first tested this out on the River Elwy in North Wales where two rivers (Aled and Elwy joined just upstream of a gauging station (Pont y Gwyddel). There was then a 2 hours travel time for the flood wave to reach St. Asaph (the town where evacuation of some residents might be needed). By setting an initial alarm at the Pont y Gwyddel river level which might occur around every 2 years, an automatic alarm warned the District Engineer to be ready to stand by, and monitor the Pont y Gwyddel level. If it reached a second Alert level, the Police would send a mobile unit to St Asaph bridge and meet with the District Engineer, who would interrogate rainfall rate at a raingauge in the area, then compare rainfall rate mm/hour with Pont y Gwyddel flow rate expressed in mm’hour, and would be able to tell if the river at St Asaph would continue to rise, or level out, or start to fall within the next two hours. Hence the name ISO-function – Inflow, Storage, Outflow. That was a very simple but effective system – it always worked OK and the District Engineer said it made him feel like God!

When it came to the Dee regulation, the upland rivers and tributaries were all quite steep with impermeable solid geology and little flood plain, all the way down to Manley Hall (near Bangor on Dee), after which there were the remains of two former glacial lakes with massive flood plain storage. So the simple translation model only had to work down to Manley Hall.

Another key feature of the Dee system with multiple sub-catchment models was you cannot rely on all telemetry systems working for 100% of the time, so there would always be some loss of data. So if we had chosen a model with complex soil storage assumptions, it would have taken longer to reach stable reliable predictions when failed telemetry started up again. However, with the ‘leaky bucket’, the forecasts could be updated in real time from the current river flow measurement which implies a soil storage associated with that river flow. Keith Beven in his book on Rainfall-Runoff Modelling described the ISO model as the forecasting model to beat, at least for small upland catchments. Later, visiting Japan, Allan found that there were similarities with the Tank Model of Masami Sugawara that was widely used there for forecasting.

Having developed the ISO-function concept for real-time flood forecasting in 1969-72, Allan undertook consultancy missions on flood forecasting for World Meteorological Office in China, Pakistan and Dominican Republic, workshops in Thailand, Mexico and South Korea, and evaluation of reports in Geneva between 1984 and 1999.

Work on Leakage from water distribution systems[edit]

Moving into Water Supply Operations in Welsh Water’s Northern Area in 1984, Allan’s remit was extended to reduction of leakage from water distribution systems, and he became convinced of the benefits of considering leakage as an untapped and (at that time) poorly managed water resource. As Water Manager of Northern Division from 1984, he linked leakage and pressure management strategies to control rules for conjunctive use of water resources, successfully navigated the 1984 drought, and achieved more rational abstraction licence conditions after detailed discussions with interested parties for three systems (two within a National Park) without objections or recourse to public enquiry. The 1995/96 droughts in North Wales were also successfully managed as Allan developed, used and promoted a concept for Welsh Water of ‘Operational Yield’ for Surface Water Yield Assessment based on behaviour analysis, which was adopted by National Rivers Authority after the 1995/96 drought.

By 1992, Allan’s research into improved leakage management practices resulted in his being seconded to the UK National Leakage Control Initiative 1992-95 as Technical Secretary, where he developed a foundation concept (Background and Bursts Estimates) now used internationally for component analysis of pressure-dependent leakage.

Following appointment as a Special Advisor on Water Resources and Leakage to the House of Commons Environment Committee’s review of the 1995/96 drought, Allan decided to concentrate the remaining 27 years of his career on international leakage management training and consultancy. He chaired the International Water Association’s first Water Losses Task Force 1995-2000, which produced the IWA International Water Balance and new key performance indicators including Unavoidable Annual Real Losses (UARL) and the Infrastructure Leakage Index (ILI), all three of which are now recognised as international best practice, and set up a successful website to provide multiple free-to-all papers to leakage practitioners. Readers of Water & Wastewater International magazine voted Allan in the top 25 for global thought leadership in the water industry in 2016 and 2017.

Information on Allan’s subsequent 27 years of multiple contributions to international leakage management since 1995 in over 30 countries are provided in the Reference Material below.


Reference Material[edit]

Allan Lambert Retirement

Allan Lambert Podcasts

Selected Publications[edit]

Lambert A.O. Catchment Models Based on ISO-functions. Journal of the Institution of Water Engineers, Vol 26, No 8, November 1972

Lambert A.O. The River Clwyd augmentation/abstraction scheme. Journal of the Chartered Institution of Water Engineers and Scientists, Vol.35, No 2, March 1981

Lambert A and Morrison J.A.E. Recent Developments in Application of ‘Bursts and Background Estimates’ Concept for Leakage Management. Journal of the Chartered Institution of Water Engineers and Scientists, Vol.10, No 2, April 1996

Lambert A, Myers S and Trow S. Managing Water Leakage, Economic and Technical Issues. Financial Times Energy ISBN 1 84083 011 5, 1998


Promoting ‘Free to All’ Open Access publication of Water Loss Management Concepts | LEAKSSuite LibraryThe ISO Forecasting Model