Kings Fleet & Falkenham IDB Abstraction

Licence Application Yield Assessment

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Conjunctive use or Farm

reservoir – yield Dependent

Current Constraints

• Estimated average yield 1500-2000Ml.

• 600-800 Ml demand for irrigation

• 1000Ml+ demand for P.W.S

• 188 Ml currently licenced

• Design year yield unknown

• Lack of local reliable flow data

• Currently two pumping stations Kings fleet and Falkenham

• Possible to move water from Kings Fleet to Falkenham

• Water Quality constraints

• Freshwater flow to Estuary

Assessing Yield

Hydrological models

Catchment Hydrology

• Available Methods include Low Flows Enterprise; NEAC model ; Catchment comparison; Rainfall run off modelling .

• Catchmod Rainfall runoff modelmost suited to this application .

• Catchment divided into hydrological zones.

• Water moves vertically through a series of conceptual stores in each zone

• Inputs Potential Evaporation and Rainfall 1970-2015.

• Calibrated with catchment observed flow data

Kings Fleet – Falkenham

model Build

Inputs

• Potential Evaporation MORECS weekly .

• 1970-2015 Rainfall Locally gauged for Calibration – Levington for P.O.R. (inc other gauges for infilling).

• Flows – gauged at Falkenham and kings fleet Pumps . Check with other gauges , Holesley, Brantham, Playford etc.

• Hydrological zones; superficial Aquifer 35%, Alluvium 32%, London clay 25%, Hard surface rapid 8%

• Single unit calibration

IDB Pump data

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Kings fleet hourly Discharge 01/01/2016 to 11/03/2015

Series1

168 per. Mov. Avg. (Series1)

24 per. Mov. Avg. (Series1)

• Significant periodicity @ 24 hour and 7 day – not hydrological – cost minimisation

• Correction required for calibration . Maximum period of 7 day selected as filter .

• Model output's reported to 7 day rolling output .

• Uncertainty regarding the more rapid response functions of the catchment .

• Local gauge and model checks indicate good accuracy of gauged data (next slide)

IDB Gauging Plausibility

checks

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run

off

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Kings Fleet & Falkenham IDB pumped cumulative runoff compared to L.F.E. Mean monthly runoff. Data shown for Time period September 2015 to March 2016 - 96 % L.T.A. Rainfall

L.F.E gauged

L.T.A. Rainfall 2015/2016 Rainfall

Series5 Poly. (L.F.E)

Poly. (L.T.A. Rainfall) Poly. (2015/2016 Rainfall)

• Early monitoring data Sep 2015 –Mar 2016 run off compared to gauge and existing steady state models .

• Sep 2015 – Mar 2016 Rainfall 96 % of L.T.A.

• Sep 2015 – Mar 2016 Measured run off 99 % L.T.A compared to L.F. E model . (95mm)

• Very encouraging checks for accurate metering .

IDB Pump Totals 2015-2016

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Cumulative Pumped Volume

Kings fleet Falkenham 2 Falkenham 1

• Total Measured

discharge 01/08/2015 to

31/06/2016. Approx.

2800000m3

• Runoff 57 % Kings fleet: 43% Falkenham

• Area 61% king fleet: 39%

Falkenham

• Rainfall Aug to June 114

% L.T.A.

Catchmod Rainfall runoff

model Calibration

• Calibrate to individual

hydrological zones .

• Soil moisture profiles

• Flow statistics including flow

duration curves .

• Catchment yield.

• Total flow

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Contribution to Flows by Area (Kings fleet)

Observed Rainfall Simulated

Area 1: Gravel crag Area 2: Alluvium Area 3: London clay

Area 4: Urban 8 per. Mov. Avg. (Observed) 7 per. Mov. Avg. (Simulated)

Total flow Calibration

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Model Fit (Kings Fleet & Falkenham)

Observed Rainfall Simulated Flow 7 per. Mov. Avg. (Observed ) 7 per. Mov. Avg. (Simulated Flow)

• 7 day rolling output to remove

periodicity.

• Removes probable urban

peaks- attenuated by storage

• Good calibration of observed

aquifer baseflow trends.

• Probable 10-15 %

underestimate of long term

average yield

• Underestimate associated with

run off from marsh area , too

high S.M.D. in shoulder months.

?

•

Catchmod calibration ‘v’

existing models. L..F E

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APR MAY JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR

Modelled Run off M3/s/km2 - L.F.E. and Catchmod

Catchmod Low Flows Enterprise

• Good calibration of seasonal

runoff with steady state

models .

• Baseflow months Consistently

10-15 % lower . Runoff

dominated months 10-15 5

higher.

• Consistent with

conceptualisation that L. f. E.

model overestimates baseflow

index @ 0.82 .

Calibration flow Duration

statistics

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Percentile

Catchmod and L.F.E. Mean Daily flow Duration curves

Modelled 1973-2015

L.F.E

model calibration 7 day

IDB gauged 7day

• Good Calibration with

observed

• Modelled and observed flow

expected to exceed L.T.A.

• Monitoring period generated

significantly more run off than

Long term 1970-2014 modelled

• Long term modelled conforms

to conceptualisation of

greater runoff and lower

baseflow relative to existing

model .

• Catchmod Modelled mean

yield believed to be 10-15 %

below actual .

Catchmod Aquifer zone

Calibration

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18/02/1982 11/08/1987 31/01/1993 24/07/1998 14/01/2004 06/07/2009 27/12/2014 18/06/2020

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Axis Title

Catchmod Calibration - Aquifer flows and Observed groundwater hydrographs

Gravel sim flows elm cottage levels

Mill lane Boyton

• Aquifer 35 % of total runoff. Major summer component .

• Longer term Calibration with local groundwater levels , extends calibration period beyond flow monitoring .

• Very good trend calibration with Elm Cottage Hollesley and mill Lane Boyton.

•

Catchmod Final

Calibration

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Kings Fleet modelled Total flow and Crag/gravel Baseflow

• Mean Daily flow data sets 1970-2015 ( calibrated to weekly)

• Winter run off more significant than other models B.F.I. 0.62 ‘v’ 0.85 L.F.E

• Vulnerability to dry winters

• Significant hard surface runoff component.

• Crag/gravel baseflow providing significant summer yield . Model believed to underestimate crag flows in dry years . Q(bf) mean = 0.025m3/sec . Probable 0.030m3/sec

• Calibration Mean run off - low 119mm, MORECS/HOST gridded 127mm (baseflow component)

IDB pumped Catchment

Design Year

• IDB estimated mean

yield 2000 Ml

• Modelled mean yield

1930 Ml

• Lowest 661Ml in 1990

• Highest 5141 Ml in 2000

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IDB POTENTIAL GROSS YIELD KINGS FLEET & FALKENHAM

Modelled gross yield

Catchmod Mean Gross yield

IDB Estimated Mean yield

Scheme Reliability

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Yield /Probability Curve - 1970-2015

Irrigation Only Scheme Multi use Scheme

• Assuming Resource can be

fully optimised. Unrestricted

infrastructure capability

• Multi use Scheme – 2100 Ml- 65

% chance of non-availability

in any year.

• Irrigation Scheme – 800 Ml - 4

% risk of non- availability.

• Irrigation Scheme – 600 Ml –

100 % reliable.

• Precautionary model

calibration Reasonable

assumption to increase dry

year yield by 10-15%

Further constraint

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Kings Fleet modelled Total flow and Crag/gravel Baseflow Design year 1995-1997

• Infrastructure to transfer

high flows.

• Freshwater flow to tide –

(S.P.A.) 0.6 Ml/day could

reduce deployable output

by 33%.

• Freshwater flow to tide

TRAC waterbody whole

estuary target. W.F.D.

assessment required .

• Salinity

• Access arrangements for

new point of abstraction .