Waye Water.

Stephen Crittenden 14/03/2008

1

A Preliminary Investigation of the Underground Water Supply at Waye. by Stephen Crittenden BSc, MSc, PhD. Independent Geological Consultant. October, 2003. Introduction. This document is a general introduction to the disposition of the groundwater source of the Domestic Water Supply at the hamlet of Waye. It is stressed that the comments and discussion in this document are made purely from surface observations by and from the best judgement of Dr Stephen Crittenden, Independent Geological Consultant. For this study no scientific measurements or tests have been performed to assess the underground water situation at Waye. Such tests, measurements and procedures may be carried out in the future. Accordingly the correctness or accuracy of the information and interpretation herein cannot be warranted and under no circumstances should any such information or interpretation be relied upon as the sole basis for any drilling or financial decision. In no event will Dr Stephen Crittenden be liable for any damages including but not limited to, indirect, special or consequential damages, resulting from the use of any information or interpretation provided. The three houses at Waye; Waye Cottage, Waye Farm and Lower Waye Farm, are each supplied with domestic water by their own dug well /cistern. Each is in the order of 10metres deep (30 – 35 feet) and at some time in the past hand dug. The three wells are approximately within 50 metres of each other. The two wells supplying the medieval long houses of Waye Farm and Waye Cottage were dug probably in the 14 / 15th Centuries in fractured / jointed rotten granite to a depth of about 30 feet (10metres). They are unlined and are about 1 yard square in cross section. The well at Lower Waye Farm is topographically lower than the other two but is also dug predominantly in granite. It is lined with dressed granite setts / bricks and was probably dug some time in the 19th century. Further investigation of this well may reveal that it is dug partially in growan /alluvium above granite. It is the occurrence of a ready supply by springs of fresh, potable water at Waye that caused it to be the site of dwellings of a settled farming community well before Medieval times. The occurrence of freshwater springs at the head of this valley of the tributary to the River Teign would have made the site attractive for human habitation. As the springs are intermittent in nature at some time in the past wells /cisterns were dug in order to store and to maintain a steady supply of water. Groundwater. It is a matter of common sense that there is a relationship between rainfall on Dartmoor, the level of water in the Fernworthy Reservoir and flow in the headwater streams of the River Teign in the Chagford area. It is also common sense that there is a relationship between rainfall and the level of water in the three dug wells (domestic water supply) at the hamlet of Waye. Observation shows that in the Spring after a wet winter the water level in the wells rises to a level substantially higher than that seen in the Summer months.

Waye Water.

Stephen Crittenden 14/03/2008

2

Rainfall water is distributed as run-off, percolation and evaporation. Run-off does not contribute to wells and springs. However, percolation does contribute to wells and springs by downward infiltration of water to bedrocks to replenish groundwater. This groundwater supplied by the infiltration of rain and snow melt is described as meteoric. Below a certain level beneath the ground surface at Waye all porous, permeable and fissured rocks are saturated with water (ie. groundwater). The upper surface of the groundwater is termed the water table. The water table surface follows in general the topography of the ground above; it is arched up beneath hills and curves down beneath hollows and vales. Beneath the ground surface three successive zones are recognized. These zones are dynamic and at Waye are very important for understanding the behaviour cycle of the water level in the three dug wells and the local spring activity patterns during the year.

a) The uppermost zone is the Zone of Non-saturation and is never completely water filled. It is the zone through which water percolates to the deeper zones.

b) The Zone of Intermittent Saturation extends from the highest level ever reached by groundwater (after prolonged wet weather), the water table, down to the lowest level to which the water table drops after drought. If the top surface of this zone reaches the ground surface then intermittent springs are formed. This can be observed at Waye, Waye Farm in particular, where a spring is used for agricultural water supply, and in the road between Waye and Tor Hill Farm (near the badger setts). The three wells at Waye are mostly in this zone and during the winter months over the last 10 years the water level at the Waye Cottage well is very close to the surface (a few feet) and drops substantially in the Summer.

c) The Zone of Permanent Saturation extends down to the limit beneath which groundwater is never found. When the top surface of this zone rises above ground level then permanent streams, swamps, lakes and rivers are formed. At present only the bottom most few feet of the wells at Waye penetrate this zone.

Simple Geology and Bedrock The storage and circulation of ground water at Waye is very dependent on the local geology. If water passes through a rock it is permeable. Permeable rocks can be porous: such as sandstones, or non-porous such as granite. At Waye the bedrock is Dartmoor Granite and is overlain by a thin veneer of soil, with in some places alluvium that has been worked for tin some time in the past and ‘growan’ – rotten decomposing granite. Granite is pervious due to the presence of interconnected open joints and fissures (both macro and micro sized) through which water can flow. The rate of water movement through a permeable rock depends on the total permeability (capacity of the rock to allow water to pass through it), the hydraulic gradient and the rainfall catchment area and can be a very low rate indeed, as at Waye. Indeed the rate of the water storage top up of the “granite aquifer” by percolation may be very, very slow. At Waye the water migrates through the rock by the most permeable routes and emerges by natural openings (to form springs and seeps), by the three artificial openings (hand dug wells) and by direct feed into the small streams. The actual water storage capacity of the granite beneath Waye is probably not high and is controlled by the density and volume of the open fractures and joints for a given volume of rock.

Waye Water.

Stephen Crittenden 14/03/2008

3

Springs at Waye The lie of the land and direct observation indicates that there are a number of spring sites in the vicinity of the hamlet of Waye. Under present climate / weather conditions these springs are mostly intermittent in nature. These springs provide some contribution of water to the headwater tributaries of the River Teign. The intermittent springs occur where the Zone of Intermittent Saturation meets the ground surface. The top surface of this zone is a water table that oscillates up and down depending upon the supply of percolating water from rainfall. This water enters joints, fissures and fractures in the massive granite and then issues where the water table meets the surface. During and after periods of prolonged drought the water table falls and the spring accordingly “dries up”.

Wells at Waye The wells at Waye were probably sited originally where there were surface springs that depending upon the climate and the weather would have been either intermittent or permanent. The wells at Waye were dug to penetrate the lower part of the Zone of Intermittent Saturation and the upper part of the Zone of Permanent Saturation thus giving a year round supply of domestic water. Shallow wells may dry up when the top of the Zone of Permanent Saturation is not penetrated. These wells at Waye would / may have flowed at sufficient water rates during parts of the year to be exploited as a continuous supply of water used to flush the down slope, shippon part of the long houses. These spring sites would have been associated with fractured and jointed rotten granite and the hand digging of the wells would have exploited these weaknesses in the granite. The ground water percolates into the well and then rises to a level that depends on the head or hydraulic pressure behind it.

Rate of Abstraction The rate of abstraction of water for domestic use from the wells at Waye are / should be regulated by a number of factors.

A. The water level in a well will fall if the “granite aquifer” is not able to transmit the percolating water to the well at the rate with which water is being withdrawn.

B. A localized cone of depression – draw down of the water table, may occur if excessive rates of abstraction are used in a well even if it is penetrating the Zone of Permanent Saturation.

C. The rate of abstraction of water through all the wells tapping the storage may be exceeding the rate at which the storage is being recharged by infiltration. This is very serious as it results in the lowering of the water table and emptying of the aquifer that may have taken decades to fill. It may then take some years for the aquifer to recharge and the water table to rise to its former level in the area.

D. It is never sensible to pump a well dry. Such a practice runs the risk of permanently damaging the water transmission ability of the fractures and fissures that ‘feed’ the well and indeed can adversely affect the water table level for some considerable radial distance from the well. Water travels by preferred routes in the fractured granite aquifer and routes can in some

Waye Water.

Stephen Crittenden 14/03/2008

4

instances become plugged /blocked such that a well may become semi-bypassed.

In the past water abstraction rates were regulated by the domestic needs of the three households and the climate / weather was such that recharge kept up with abstraction. However, modern day living – daily baths/showers, washing machine, dish washers, flushing toilets - and climate change have combined to make the domestic water supply to the hamlet of Waye a problem. The water level in the three wells is as low as it has ever been, in the last 20 years at least, and there is no oral history (or indeed no written history that I have seen) of any of the wells at Waye ever running dry. Water for agricultural use was supplied by springs outside the domestic curtilage of the farm buildings and regulated by abstraction licenses. This summer of 2003 has been exceedingly dry and the pattern of climate change would indicate that dry summers will be the norm for the future. Over the last decade or so summers have become progressively drier and the amount of annual precipitation has been decreasing. Accordingly care must be excercised now and in the future, in the amount of the water abstracted from the wells for domestic use at Waye. The aquifer must be allowed to recharge, if possible, back to its former levels. This can be gauged empirically by seeing how far the water level in the wells rises this winter, assuming we receive a good amount of rain and / or snow. The danger will be then that the domestic users of the water will relax and be less vigilant in their care of how much water is being used each day. It is apparent that the sustainable domestic use of the water from the three wells is far below the maximum domestic abstraction limits of 20 cubic metres / day per well set by the Department of the Environment (equivalent to 4,400 gallons / day per well). A typical well in Granite in Devon usually flows less than 3 – 4 cubic meters /day. Accordingly each of the dwellings at Waye must take care in their domestic water use so as not to violate /derogate any of the protected domestic water rights of their neighbours.

Remedies The immediate remedy is to restrict water consumption from the three wells to domestic purposes only. This domestic use at each household can be reduced by a number of simple measures.

• Turn off taps while using a basin thus not allowing the water to run to waste. • Minimise the use of a dishwasher – if used then only use with a full load. • Minimise the use of a clothes washer – if used then only use with a full load.

Preferably use the launderette in times of drought! • Take showers not a bath. • Collect rainwater in a butt or butts and use for garden if need to do so. • Place a brick in the lavatory cistern to reduce the amount of water used per

flush. • Refill the lavatory cistern with a bucket of water from the rain butt. • Wash the car at the ‘car-wash’ in Okehampton.

Waye Water.

Stephen Crittenden 14/03/2008

5

Other remedies are not simple but aim to increase and secure for the future the domestic water supply for Waye in some way. Three alternatives are summarized (but not costed or risked) as follows:

• Dig each well deeper into the Zone of Permanent Saturation. I am not clear how this could be accomplished but it would be a ‘messy’ job and would rely on the newly dug section of well intersecting water filled open fissures, fractures and joints. The water would have to be drinkable. How high the water level would then rise in the well would depend upon the hydraulic gradient in the granite reservoir. This deepening of the wells at Waye would make downhole pumps necessary to ‘lift’ the water from the wells to the surface. Downhole pumps are expensive and take up space so the wells would have to be deepened considerably. At present water in the three wells at Waye is lifted to the surface by pumps at ground level. Pumps draw water by suction. The pressure at the inlet (the foot valve) is reduced below that exerted by the atmosphere on the surface of the water so that water is forced through the inlet valve and up the suction pipe. If pump suction pressure were at absolute zero the greatest height to which atmospheric pressure would force water would be about 34 feet. This is the limiting height at which a pump is set above the lowest water surface (ie Summer level) in the well and for practical purposes is about 20 – 25 feet. The present (Sept / Oct, 2003) water level in the well at Waye Cottage is about 26 feet below the pump.

• Drill a borehole or boreholes at Waye into the granite deep into the Zone of Permanent Saturation. The hope would be that a number of fresh and drinkable water bearing fissures, fractures and joints would be intersected by the well bore thus providing multiple sources of water influx into the well bore. The location and the number of boreholes to be drilled are open to investigation and debate and a thorough site survey would need to be done to assess existing water rights, contamination possibilities etc etc. Various permissions (if necessary) would have to be sought for the siting and drilling of a borehole and for the eventual abstraction of water. If a deep (about 65metres) borehole were drilled then the chances of obtaining water are good but….how much water and of what quality cannot be determined. It is no good drilling boreholes if the water is not drinkable (or would be expensive to treat). Boreholes supply good drinkable water at nearby farms; I believe at Thorn (Michael Stanbury) and at Waye Cross (Mark Loram). The depth, type and flow rates of these two boreholes and any others nearby need to be established before meaningful comparisons can be made with Waye. The borehole drilled at Tor View Farm (Richard Knox) at Whiddon Down supplies a large quantity of iron rich water that is not fit for human consumption; it goes to the pigs I understand. This high level of iron I believe may be due to the fact that the aquifer penetrated is metamorphic Culm Measures and not granite. This will have to be confirmed. The hamlet of Waye is underlain by growan and alluvium, rotten granite and hard ‘blue’ granite; not by Culm Measures or the metamorphic aureole. Interestingly at Waye there is the possibility that a borehole could be sited such that it taps two sources of water; one from an overlying alluvial aquifer where the water is possibly more mobile and thus prone to contamination and one from the granite aquifer beneath. The thickness and extent of the alluvial deposits to the north and north east of the hamlet need to be determined.

Waye Water.

Stephen Crittenden 14/03/2008

6

• Connection to the South West Water supply system is a possibility as the nearest main is I believe approximately 700metres west of Waye Cottage. A connection would guarantee a good supply of high quality domestic water; but at what price?

Stephen Crittenden October 30th, 2003.