Piezometric dipwell groundwater monitoringMonthly monitoring has been undertaken of the network of piezometer dipwells on the fen, which now total 54 in number.
Records date back to the late 1970's and give an excellent, detailed data set.  The wells include ‘near-surface’ wells set in

peat, shallow ‘Drift’ tubes set in sands and gravels under the peat surface, and‘chalk’ wells set deep into the underlying chalk
rock.  Some are paired with the permanent vegetation monitoring quadrats.  In addition, gauge boards on the main river sluices are also recorded on the same day.  

A trend chart for chalk piezometric groundwater levels can be seen below.

Rainfall Monitoring
Rainfall is also recorded on a monthly basis, always on the same day as the piezometric dipwells. 
The fen rain gauge is  sited on Middle Fen.  A chart showing annual rainfall totals for the last few years can be seen below.

Nutrient Monitoring

Water Quality Monitoring

Water quality monitoring was established in February 2004 following initial work undertaken by EA in 2000. 

The field sampling currently follows a bi-monthly collection with equipment available to undertake sampling of storm water

flows in both river and catchment drains.  Methodology and determinands tested can be seen below along with a map

showing the locations of the sampling points within the reserve.

Sampling Strategy for Water Quality Monitoring Work

Water samples are to be collected at fixed frequencies throughout each year.  The sampling programme is shown below:

3 river locations to be sampled on the River Waveney bi-monthly (looking at 5 determinands for 5 sampling months

of the year, and then at 12 determinands for one sample month*). Locations will be (a) upstream of all notable external

drain inputs, (b) downstream of one notable drain input, and (c) downstream of the second notable drain input.

These sampling locations also have the benefit of being approximately at ‘thirds’ down the extent of the valley comprised

by the fen, so comparisons and contrasts can be made on water quality in the river adjacent to each ‘third’ of the reserve.

7 aquatic fen areas to be sampled every 4 months (looking at 5 determinands for 2 sampling months of the year, and

then at 12 determinands for one sample month*).

2 Internal Drainage Board Drain (IDB) locations and 2 river locations to be sampled 4 times each year, at least

once coinciding with a heavy precipitation event and once following a prolonged dry period (following recommendations

detailed in pilot study on the fen in 1999-2000).

The River Waveney, looking downstream from Lang Fen

Total nitrogen (TN)
Total oxidised nitrogen (TON)

Suspended solids (SS).

’12 determinands’ represents –

Total phosphorus (TP)

Soluble reactive phosphorus (SRP)

Total nitrogen (TN)

Total oxidised nitrogen (TON)

Ammonia nitrogen (NH4-N)

‘5 determinands’ represents –

Total phosphorus (TP)

Soluble reactive phosphorus (SRP)

Calcium (Ca)

Sodium (Na)

Potassium (K)

Total iron (Fe)

Sulphate (SO4)

Chloride (Cl)

Suspended Solids (SS).

Monitoring Dry Deposition of Ammonia (NH3)

The fen represents one of the UK sampling stations for monitoring atmospheric levels of ammonia in dry precipitate

form (NH3).  The scheme is part of the National Ammonia Monitoring Network (UK NAMN) which was run by the

Institute for Terrestrial Ecology (ITE) since its inception in 1995 (Now the Centre for Ecology & Hydrology - CEH). 

Three passive ‘alpha’ tubes sample the concentrations of dry ammonia in the air, recorded as ug/m3 & are sent to CEH

in Edinburgh each month, being collected on the same day as hydrological recording above (typical levels at the fen

range from 2-7 ug/m3).  Combining these totals with background gaseous NH3 levels and with a prediction model for

the area, gives an approximate total annual nitrogen load to the fen as 25-29 kg/ha/yr. 

The ammonia monitoring station at the fen

The unusual metal strips on the collection cover

deter birds from landing and corrupting data!

Critical/Threshold levels for sensitive wetland sites

Critical loads for nitrogen deposition have been estimated using a wide range of approaches, but it is most simple to compare

recorded results with the 'empirical critical loads' as revised by the UNECE in 2003.  In the latest revision, the critical loads

(kg-N/ha/yr) for different habitat types are set at:

Calluna dominated wet heathland: 10-20 kg N/ha/yr

Erica tetralix dominated wet heathland: 10-25 kg N/ha/yr

Poor Fens: 10-20 kg N/ha/yr

Rich Fens: 15-35 kg N/ha/yr

The annual loadings of N on the fen strongly suggest that the nitrogen critical load is exceeded, and that the fen is at risk from

N deposition.

The project is set to continue for the foreseeable future until a detailed picture is obtained for the whole UK.  The Waveney

and Little Ouse valleys typically have high concentrations of NH3, associated with agricultural practices such as intensive

outdoor pig and poultry farming in the local area.