Dr Pe P t er Co C o o m o b m es

Transcription

1 Dr Pet er Coombes

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5 Uyun D1.6 D1.5 D1.4 D1.3 D1.2 Mubarraz D1.1 D1 Qarn Shabah Kilabiyah D1 D2 Umran D2 D2.2 Jishshah Al Oyoun Lake D2.1 Al Asfar Lake The irrigat ion syst em has low ef f iciency Al Asf ar Lake is reliant on excess irrigat ion wat er Irrigation water discharges to the D2 drain The D2 drain discharges to Al Asfar Lake Al Asf ar Lake also receives wast ewat er and leakage f rom ot her wat er syst ems Hofof Taraf

6 14,800 ML 12,600 ML Losses Lake Al Oyoun Recycle Losses 78,800 ML 123,200 ML D1 drain Irrigation 52,800 ML Losses Rain Evaporation Losses 62,400 ML 5400 ML 6340 ML 1,210 ML 38,500 ML Wastewater treatment plants 65,700 ML 502,000 ML Recycle D2 drain Lake Al Asfar Domestic Water Supply 116,800 ML Aquifer 500,000 ML 43,800 ML Recharge Losses

7 HI DA observes dept h and velocit y of f lows in drainage syst em. Measurements every two weeks Observed dept hs used wit h inf ormat ion about inf rast ruct ure A hydraulics model was used t o det ermine inf lows int o Al Asf ar Lake

8 11,000 10,000 9,000 8,000 7,000 6,000 5,000 4,000 3,000 2,000 1, Month

9 Ar ea and volumes of t he Lake syst em measur ed using Satellite positioning, Direct measurement of water depths Field inspections Measur ement s used as gr ound t r ut h f or dat a f r om t he NASA Digital elevation data obtained from the Shuttle Radar Topography Mission (SRTM)

10 Locat ion of survey point s

11 The Al Asf ar Lake syst em is a series of perched lakes The upper (Summer) lake f ills and overf lows int o t he lower (Wint er) lakes A cascading syst em

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13 Height above sea level (m) Summer Lake Area (km 2 ) Volume (ML) , ,700 Wint er Lake , , , , , ,700

14 25,000 20,000 15,000 10,000 5, Months since Dec 2006

15 70,000 60,000 50,000 40,000 30,000 20,000 10, Months since Dec 2006

16 Al Asf ar Lake operat es as a syst em of cascading perched lakes The upper (Summer) lakes overf low int o t he lower (Wint er) lakes The behaviour of t he lakes varies wit h seasons in response t o climate, inflows and rainfall During t he period 2007 t o 2010: Summer Lake: Volumes varied f rom 9, 190 ML t o 22, 850 ML. Average dept hs ranged f rom m t o m Area ranged from 11 km 2 Winter Lake: to 19.2 km 2 Volumes varied f rom 6, 180 ML t o 59, 500 ML. Average dept hs ranged f rom m t o m Area ranged from 8 km 2 to 22.4 km 2

17 The maximum area and average dept h of t he Al Asf ar Lake system are: 78 km 2 6 metres Stormwater runoff created by storm events also acts to occasionally fill the lake system

18 The Al Asf ar Lake is an est ablished and f unct ioning ecosyst em The Lake receives high pollut ant loads including: Nit rogen, Phosphorus, BOD, Salinit y Evidence of resilience t o t he pollut ant loads Abilit y t o repair some of t he damage The reed lake improves t he qualit y of wat er These loads drive t he pot ent ial det eriorat ion of t he lake s ecosyst em Oxygen deplet ion, generat ion of t oxins and algae The lake is challenged by wat er qualit y loads I mproving t he qualit y of t he input s will allow t he Lake t o repair it self

19 A concept ual design a t reat ment t rain t o improve t he qualit y of inputs to the lake a. Remove gross pollutants and litter (capture) b. Remove sediment s and BOD (set t lement and f ilt ering) c. Remove nut rient s and BOD (oxygenat ion and f ilt ering

20 The Treat ment Train Removal of lit t er Set t lement Filt rat ion Oxygenat ion Cascades with reed Islands Buffer strip (reeds and macrophytes) Rock filter Floating boom litter trap Cascades with rocks Modified clarifier D2 Drain 50 m 100 m 200 m Waste processing area 100 m Highway Waste processing area 500 m Oxygenation pond with macrophyte islands To Al Asfar Lake

21 Litter boom Clarifier Rock cascade Reed cascade Reed island oxygenisation pond D2 Drain Rock filter Reed filter Uses dept h of f lows, kinet ic energy and velocit y The cascade of wat er removes cont aminant s Litter boom removes sone of the litter Clarif ier removes larger sediment s and some of t he BOD The rock cascade and filter removes smaller sediments whilst introducing oxygen to the water The reed cascade and f ilt er removes t he maj orit y of BOD and nutrients The oxygenation pond polishes the water prior to the existing reed lake

22 Al Asf ar Lake is an est ablished and f unct ioning ecosyst em There is suf f icient wat er available f or Al Asf ar Lake Dependent on surplus irrigat ion wat er and input s f rom t he Al Hasa region However, t he viabilit y of t he Lake is challenged by pollut ant loads f rom t he D2 Drain This problem can be remedied by changing t he qualit y of inf lows t o t he Lake using a Treat ment Train More ef f icient in t erms of t ime and economy t han changing t he Lake

23 This proj ect has: developed an underst anding of t he hydrology and wat er qualit y processes in t he Lake syst em Designed a concept ual t reat ment t rain t o rest ore t he Al Asf ar Lake system The Al Asf ar Lake is a syst em of perched lakes t hat cascade t o lower lower lakes The proposed t reat ment t rain can be delivered wit hin a t wo year period. I t is likely t hat subst ant ial improvement s in t he Al Asf ar Lake syst em will be experienced wit hin 2 t o 5 years response t o t he proposed program.