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NEWBOURNE SPRINGS S. LINFORD-WOOD At Newbourne, groundwater discharges from the Red Crag via many discrete and diffuse issues at, or just above, the junction with the underlying London Clay. This occurs at an elevation between 10 m and 12 m above ordnance datum. As the Crag has such a productive yield of groundwater, it is considered an aquifer. It is dominated by intergranular flow, being comprised of shelly sands in its lower saturated part. The porous nature and consequent storage properties mean the groundwater system is well damped and tends to support a reliable perennial discharge with modest seasonal variation. These favourable characteristics led to the springs being used for water supply purposes.

The pumping station at Newbourne springs was established by the Felixstowe & District Water Company before the First World War. At the time of the 1963 Water Act, the abstraction from the springs was up to 4,530,000 gallons per annum. This was provided by a single pump of capacity 24,000 gallons per hour that was permitted to deliver a maximum of 576,000 gallons per day for supply. Total flow from the springs was monitored routinely at the gauging station that can still be seen in the Nature reserve.

Between 1974 and 1984, daily mean flow was measured at 0·031 cumecs equivalent to 31 l/sec. The minimum average daily flow recorded over this period was 7 l/s and the maximum was 86 l/s. The annual abstraction for potable supply was only approximately 2 % of total annual spring flow.

Spring catchment area Interestingly, the drainage area to the springs is only 8·1 km2, which, on the basis of an annual recharge of 50–80 mm, would be expected to yield a discharge of 648,000 m3/annum. This is equivalent to an average spring flow of 12–20 l/s. However, this is only 33–60% of the actual flows recorded, even though there is also abstraction of groundwater for agricultural use in the surrounding catchment. The reason for this apparent anomaly is that the surface water catchment does not reflect the groundwater catchment to the spring. This is significantly larger and it appears that Newbourne spring owes its permanence to the unusual morphology of the London clay surface. The spring is simply a surface manifestation of this hidden geomorphological control.

If the borehole logs for the surrounding area are consulted, it is evident that there is in fact a large shallow basin structure in the London clay surface that can be traced westwards from Newbourne to Foxhall Heath covering an area of approximately 12 km2. The London Clay is an aquiclude – a rock of low permeability – and, as it underlies the Red Crag, causes the lower regions of the overlying formation to become saturated by infiltrating rainfall. The form of the basin is such that groundwater is directed eastwards under prevailing groundwater gradients towards the lip of the basin at Newbourne.

Only under exceptionally high ambient groundwater levels does some water over-top the concealed basin and discharge southwards via other diffuse and discrete springs into the Mill river.

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The volume of groundwater stored in this basin can be estimated at about 3·6 mm3. Hence, for any single year the spring discharges at Newbourne represent approximately 7–10% of the groundwater in storage.

The Red Crag aquifer typically has a horizontal permeability of 10–20 m/ day and an effective porosity of 10–15%. Close to the springs at Newbourne, the linear velocity of groundwater is of the order of 2–4 m day. However, from the western extremity of the basin, hydraulic gradients are very shallow and groundwater will be travelling for several hundred years before it finally emerges at Newbourne.

Groundwater quality The quality of groundwater at Newbourne is intimately associated with the agricultural land use in the catchment. The soils of the surrounding area are characterised by light, free draining brown sands of the Newport 2 Association and similar finer silty derivatives called brown earths. They are developed on glacial-fluvial outwash deposits of the Kesgrave formation that are comprised of quartz and flint rich sands and gravels. The organic matter content of the soils is low and they are droughty, naturally acidic and readily leachable.

Historically, the acid heathland vegetation that dominated the area has been gradually replaced by arable farming supported increasingly by irrigation.

These are soils from which nutrients are easily leached and, consequently, land use change has promoted increasing nitrate concentrations in groundwater. A significant amount of this nitrogen was released by the historical ‘ploughing up’ campaigns for food production for First and Second World Wars, but increasing arablization, and subsequent losses of agricultural fertilizers from modern farming, have added to this loading. The Public Water Supply at Newbourne was affected by high nitrate concentrations that were evident even early in its period of operation. Public water supply use ended in the 1980s when limits for nitrate in drinking water were revised. This limit is currently 50 mg/l.

Today, Newbourne springs have nitrate levels (as nitrogen) averaging 156 mg/l – three times drinking water standard. There are no significant natural mechanisms in a sandy aquifer that will promote denitrification. The groundwater is slightly alkaline in character at pH 7·8 when it discharges from the springs and the water type is calcium-carbonate-chloride. This expresses the predominant dissolved ion composition. The buffering of the groundwater has been achieved by the dissolution of calcareous material within the aquifer and suggests that decalicification of the Red Crag continues. Typically background chloride values in the Crag and Chalk aquifers in Suffolk range between 30 and 50 mg/l. At Newbourne, the levels are about 70–100 mg/, much higher than can be attributed to elevated chloride in rainfall associated with the proximity to the coast and probably reflects partly the impact of fertilizer use.

There is currently no evidence of any herbicides or pesticides above detection levels in the groundwater from the spring discharges. Most agricultural herbicides and pesticides used today decay rapidly in the soil and unsaturated parts of the aquifer and tend to be attenuated before entering the groundwater. The absence of synthetic organic substances also attests to the

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effectiveness of the nature reserve around the spring in protecting the quality of groundwater. These ‘protection zones’ around springs are not a recent introduction. The value of adopting such measures to secure a spring from biological pollutants and farm manures was well recognised by the Victorians and applied, for example, to the Lexden Springs in Colchester in 1890s.

Simon Linford-Wood Environment Agency Iceni House Cobham Road Ipswich, Suffolk IP3 9JE

FIELD REPORT R. DIXON The aim of the field excursion was to examine the geology and geomorphology of the geosites in Newbourne, based mainly in the Suffolk Wildlife Trust Nature Reserve of Newbourne Springs. Bob Markham led the trip, but was assisted by GeoSuffolk members located at points around a circular walk to demonstrate particular features. The group included several members of the Suffolk Naturalists’ Society, as well as those attending the RIGS presentations. The site has been visited before by SNS members and pupils at Amberfield School on educational visits.

The group met at the visitor’s centre car park (TM274432) and were directed northwards to the flume gauge (TM273433), where Caroline Markham explained the flow characteristics of the stream and described project work that has been carried out here (see for example White Admiral No 40, p. 19).

Upstream from the gauge, comminuted Red Crag shells could clearly be seen in the stream bed, and fluvial processes observed. Small scale ripples, highlighted by contrasting coarser pale sandy crests and dark organic finegrained troughs, are common in the stream bed.

Barry Hall was located further north (TM270436) to indicate the several springs in the vicinity. The valley sides steepen appreciably here as the result of active spring sapping and undercutting where the springs emerge at the Red Crag/London Clay junction. Pools are littered with Crag shells that have been washed out of the Crag by the spring water. Peat is actively being formed today on the valley floor.

Returning a short way, the route led along the public footpath across the valley, on the western flank of which ample evidence of Red Crag – shells and phosphatic nodules – from post and rabbit holes, up-rooted tree stumps and elsewhere. From vantage points, it is clear that the vegetation is directly related to the geology and its drainage, with heath and dry woodland occurring on the Red Crag, alder carr, fen and reed beds on the London Clay and alluvium.

The walk continued along Fen Lane, past Fenn House, where excavations in 1985 for a pond revealed peat layered with ‘crag wash’ from streams, and on to Crag Cottage, behind which are old Crag pit faces with good cross bedding and yielding Glycimeris-Venerupis shell gravel assemblages.

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The last stop on the circular walk was to inspect the external fabric of St. Mary’s Church. Although mainly of brick and flint, much use has been made of calcareous mudstone septaria from the London Clay. Many of these blocks show evidence of modern marine borings and impressions of limpet attachment, indicating that it was obtained from the foreshore of the Orwell or Felixstowe area, where it outcrops. Shelly Red Crag pebbles and possibly some Coralline Crag can be seen in the early C15 tower, and various limestones can be found here and there. The east wall of the chancel was destroyed by the great storm of 1987, but rebuilt using mortar containing shelly Red Crag, with whole Astarte, Cardium angustatum, Mya arenaria and other molluscs clearly visible.

Roger Dixon was positioned at a small Red Crag face - all that remains of once huge ‘Great Pit’ (TM275433). The base of the pit lies on London Clay and springs drain into a large pond. Some five sets of medium-scale ripples are found in the Crag face, with well-formed sedimentary structures such as smallscale ripples, mud drapes and shell imbrication. It is interpreted as being deposited in a shallow tidal sea, with current velocities up to 0·6 m/sec towards a generally south-westerly direction, in a water depth of 10m or so.

The fauna is dominated by Spisula ovalis, with species of Macoma, Cardium, Venus, Astarte, Mytilus, Arctica, Glycimeris, Buccinum, Nucella, Turitella and many others being found by members. A small fault and other fractures can also be seen.

The group left the car park for a final stop at Newbourne Hall, where sawn blocks of Coralline Crag, the remnants of once more extensive use, are used as a building material in the west wall. These may have been quarried at Sutton Knoll, only some 3 km away on the opposite side of the River Deben. A few bits of bone were found on the drive, coming from post holes dug into Red Crag on the estate. Mr. J. Somerville, the owner of the Hall, kindly showed us some of the Crag material in his possession, including a fine specimen of Cassis saburon from a Boxstone found at the base of the Red Crag from one of the holes, and to whom thanks are due for allowing the group access.

This was a rewarding afternoon, with much to observe and where the relationship between geology, landforms, drainage and vegetation can clearly be observed. Bob deserves hearty congratulations for his splendid efforts in organising the excursion.

Roger Dixon The White House 7 Chapel Street Woodbridge Suffolk IP12 4NF

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