Art. 13.—Water-conservation and Hawke's Bay Artesian Systems.

Transactions and Proceedings of the Royal Society of New Zealand, Volume 54, 1923, Page 134

Art. 13.—Water-conservation and Hawke's Bay Artesian Systems. By H. Hill. [Read before the Hawke's Bay Philosophical Institute, 26th November, 1920; received by Editor, 24th November, 1921; issued separately, 12th February, 1923.] On frequent occasions I have had the honour of bringing under the notice of the Philosophical Society the question of artesian wells and systems of wells.* See Trans. N.Z. Inst., vol. 20, pp. 282–93, 1888; vol. 22, pp. 429–38, 1890; vol. 37, pp. 431–44, 1905. Not merely in Napier and over the Heretaunga Plain as far as Pakipaki are flowing wells to be seen, but also at Otane, at Ongaonga (on the Ruataniwha Plain), at Wanganui, at Palmerston North, at Poverty Bay, and other places. As settlement and population increase, so also do regulations multiply affecting the rights and duties of citizens. Water being one of man's essential wants, the duty of every local and governing authority is to pay heed to providing a suitable supply of potable or drinkable water; and, if a manufacturing community, also water suitable for the fostering of manufactures. Since my first paper on the artesian-wells system of the Heretaunga Plains the town of Napier has increased in its population to a fair extent, and perhaps the settlement of population over the plain has increased even to a larger extent. In the year 1887 Napier was supplied with water by means of six artesian wells, four of them having a 3 in. bore and two a 2 in. In July, 1917, a return was presented to the order of the Borough Council giving a list of nineteen wells supplying water for public use—two wells of 6 in. bore, two wells of 4 in., and seven. of 3 in. These wells were returned as varying in flow from 20 to 10,000 gallons per hour. In this return the best flowing wells are given as being situated in Nelson Park, in Sale Street, and at the junction of Munro Street with Raffles Street. The total flow from the nineteen wells was said to be 1,730,100 gallons per day, weighing nearly 8,000 tons. Since the return was made a number of other wells have been driven to the order of the Council. Up to the end of January, 1919, new bores added more than half a million additional gallons to the borough supply. Thus, assuming that no falling-off in the quantity of water from the wells as returned in July, 1917, has taken place, the daily supply of water to the Napier Borough should be 2,210,000 gallons. If the present population of Napier is 15,000 (an overestimate) the supply represents more than 145 gallons of water daily for every man, woman, and child in the town. The number of artesian flowing wells that are supplying the water requirements at Taradale, Meeanee, Farndon, Clive, Awatoto, Hastings, Mangateretere, Havelock, and Pakipaki must be very great. In the year 1887, at the time when six wells sufficed for the Napier Borough supply, it was estimated that not fewer than three hundred wells were to be found over the whole of the plain area outside Napier. Thus in the Borough

of Hastings, where no local scheme of supply then existed, more than ninety wells were known to be in use, and on the lands owned at that time by Messrs. J. H. Coleman, J. D. Ormond, J. N. Williams, and T. Tanner there were more than fifty wells. Assuming the number of artesian wells put down in the Heretaunga area has merely increased in the same proportion as those in Napier during the interval, then the number of wells over the plain and in various towns and townships would exceed 1,100. I do not think this estimate in any way excessive. There is, however, a difference in the diameter of the wells put down. For domestic use the wells are usually a 2 in. bore, and for manufacturing requirements a 3 in. bore, the exception being the riverside well at Farndon, where there is a 6 in. bore for wool-scouring purposes. Taking the wells throughout the plain area as averaging a 2 in. bore, and that the flow of the wells is proportionate to the flow in the Napier wells, then, if a 4 in. bore gives a flow of 6,000 gallons per hour, a 2 in. well under similar conditions will give 1,500 gallons an hour. Hence 1,100 wells flowing at the rate of 1,500 gallons an hour for each will every day yield 29,600,000 gallons. The annual yield, if spread over the surface, would represent an annual rainfall of 7 in. over the 80,000 acres of plain. According to the analysis of the water from nineteen different wells, it is shown that in every 100,000 gallons of water there are 20 gallons of

solids held in solution. In the Napier wells, and estimated on the flow already stated, there are 440 gallons daily of solids brought to the surface, or 951 cubic yards in a year. So also on the same proportionate estimate of solid contents in the supposed 1,100 wells over the plain area, 17,130 cubic yards of solids are brought to the surface in solution in the course of the year. The general purity of the water as determined for Napier is in every respect satisfactory. It would be well, however, to have its actual hardness determined. The receiving tanks or basins into which the water flows from the different wells tell their own story as to the sand, shingle, and other material that is brought to the surface, and unless there is replacement of the material that is withdrawn with the water in suspension and solution the overlying pressures will in time bring about altered conditions in the water-bearing beds. Creeps are certain to occur. They may at the present time be hardly appreciable, but experience can be quoted of important changes taking place in various wells both in Napier and the plain area, and I do not doubt, if only proper records were kept, some surprising results would be available. The facts that have been obtained as to the varying depths of the artesian wells in different localities enable a section to be drawn showing the deepest line of water-supply over the plain, and so also showing where the valley shallows and the wells diminish in depth. A knowledge of the facts is necessary to the proper determination of the water-flow that is of so much value to the community. The surface of the plain itself presents some surprising and interesting features, and especially so when considered in relation to the depth of the wells. The plain at Roy's Hill, on the left of the Hastings-Maraekakaho Road and opposite the junction road to Fernhill, is 166 ft. above sea-level, and is almost south-west of Scinde Island. Taking this as the highest point of the plain, the following heights are of interest. The height of Omahu, at the bridge across the Ngaruroro River, is 73 ft., and at the old mill on the Redcliffe Road it is 45 ft. At the Tutaekuri River bridge, Redcliffe, it is 34 ft., and at Taradale, at the junction of the roads near the post-office, it is 16 ft. At Pakipaki it is 32 ft., and midway between Hastings and Pakipaki it is 41 ft. At Havelock, at the bridge on the Hastings Road, it is 34 ft., and at Hastings, at the railway-crossing, 41 ft. At the junction of the Napier-Havelock and Napier-Hastings Road at Mangateretere it is 15 ft., at Pakowhai 18 ft, and at Meeanee 9 ft. These heights show the gradual slope of the plain, and it is possible to follow the old river-valleys as the rivers meandered over a swampy surface that every flood modified and increased. Few wells other than those in the Havelock Township are situated on the plain at a higher elevation than 40 ft. to 45 ft. In putting down a bore on higher land the water in the tube may rise to a level representing 40 ft. or a little more above sea-level, but no flowing wells are obtained on the plain area higher than this. Some years ago Mr. R. D. McLean put down a trial bore in the vicinity of his Maraekakaho property, but no flow was obtainable. I believe, however, that water rose in the pipe corresponding to the height of the water-table, as in the case of the artesian wells. It is interesting to note the altering depth of the wells between Pakipaki and Napier—the line representing the deepest portion of the old valley, or, in other words, the trough. At Pakipaki, towards Pukahu, the wells vary from 70 ft. to 100 ft., and to 125 ft. towards Longlands. These places are about 40 ft. above sea-level, so that the water

is found from 40 ft. to 50 ft. below sea-level at Pakipaki, somewhat deeper at Pukahu, and 25 ft. or more still deeper at Longlands. Hastings has an excellent well that is 230 ft. below sea-level, and in Napier there is a well that is 397 ft. below sea-level, the water from which flows 26 ft. above the surface. These facts show the general depth of the water-bearing beds in different parts of the plain, but, unfortunately, no scientific work has yet been done in the way of mapping the water-bearing area, because it is only in exceptional cases that a trial bore is put down to test a deeper area for a fresh water-bearing bed. It would be folly to assert that another water-bearing bed is not possible in certain places over the plain. In Napier a trial bore went down some years ago to the depth of 743 ft., and the river-alluvial had gone. So also at Greenmeadows the late Mr. H. Tiffen put down a trial bore to a depth of 600 ft., but after the first 100 ft. the pipe went into the blue fossiliferous clays that are exposed in the district underlying the limestones, and there was no water-result. But when more consideration is given to the conservation of water the number of water-bearing beds will be known throughout the plain area, and it will be possible to discover any alterations that are taking place in the closing or blocking of beds, and it may possibly come about that the actual sources of supply will be found, which at present are mere matters of surmise. For many years this question of artesian water-supply has been studied by me, and records have been kept in the expectation that the time will come when the facts that have accumulated will lead public bodies to unite in the utilization and scientific development of their water-supplies. At the present time each district provides in its own way for its own requirements. Napier, Taradale, and most of the plain area are entirely dependent on an artesian water-supply. Hastings, however, and, I believe, Havelock, have each a gravitation supply. Much attention has been given in the United States to the scientific study of artesian wells and to the causes leading to their exhaustion, which has occurred in various districts. The following quotation is taken from the United States Geological Survey water-supply and irrigation papers:— “It must be kept in mind that there is a limit to the amount of water that can be withdrawn from an artesian basin. There is no such thing as an inexhaustible supply in this connection. The amount of water available is limited, on the one hand, by the amount of rainfall upon the catchment area and the facility with which the rainfall can obtain entrance to the porous stratum, and, on the other hand, by the capacity of the water-bearing rock to transmit the water over long distances and the diminution through leakage and seepage. These two limiting conditions are usually of sufficient magnitude to render the overdrawing of the supply a practical and present danger which should be constantly kept in mind.” These are words of wisdom, and are based on an experience which has not yet occurred in this Dominion, though there are many symptoms of a diminishing pressure in a number of wells both in Napier and over the plain. In scores of instances it is found that the head or water pressure in a water-bearing area is constantly lowering where large quantities of water are being borne away. Underground supplies are limited as to quantity of water available, just as a river is limited by the supply of its tributaries. There is now and then an apparent clogging of the water-bearing rock in the immediate neighbourhood of the well. Whether the clogging

is due to the deposit of fine silt in the pores of the rock, or to a microscopic growth of plant-life, or to a gelatinous deposit of iron, has not been determined; but the withdrawal of solids in solution and suspension in the water is sufficient cause to account for a large diminution of flow in a given area, even though the quantity of water has not apparently diminished. The putting-down of a large number of wells naturally leaves spaces where formerly was a water-channel full of water. The spaces increase as every bore is driven into the water-basin. A well put down in Munro Street between May and August, 1888, was said to have struck water at 183 ft. The well was a 6 in. bore, and large lumps of clay were thrown up, and soon the well brought to the surface nothing except blue sand in a discoloured water. In the course of a day or two the street in the vicinity of the well was covered with sand. The cause being discovered, the pipe was driven to a depth of 196 ft., when the sand ceased. More than 110 loads of sand were carted away from about the well, and certainly it did not represent one-half the quantity brought up. It can be understood what the effect the withdrawal of so much sand must have upon the adjacent overlying beds. The pressure would in the course of time bring about creeps, and the well, which cost nearly £300 to put down, was soon after abandoned, it having become choked. In addition to the wells put down in Napier under the direction of the borough authorities, others have been undertaken by private persons or companies. Some years ago the borough authorities had a well driven to a depth of 743 ft., and Robjohns and Co. went down 753 ft. in the hope of striking water, but both were unsuccessful. The deepest flowing well in Napier is 404 ft. The flow is excellent, and when water was struck it rose 26 ft. or more above the surface. In this same well a water-bed was passed at 240 ft., and another at 337 ft. There is a good flowing well at the gasworks, the depth being 229 ft. The wells that make up the borough supply are scattered irregularly over the flat area, but the present system causes great loss in the flowage of water from the different wells, on account of imperfect reticulation. The wells put down along Munro Street indicate the general dip of the underlying beds, and act as a guide to the tilt of the water-bearing bed in the vicinity of Napier. Thus, in Munro Street, 24 chains from the foot of the hills is a well 166 ft. deep; 14 chains farther along the street is another well, 196 ft. deep; and 20 chains farther along, near the junction of Munro Street with Hastings Street, is another, 240 ft. deep. This gives a deepening in the water-bed of something like 2½ ft. in every chain along the street towards the south by east, and no doubt the deepest wells will be found near the railway at the corner of George's Drive. The wells put down in Nelson Park, and subsequently in McLean Park, appear to have seriously interfered with the flow of the smaller private wells in the immediate neighbourhood, and some of the latter have even ceased to flow. This is sufficient evidence pointing to the limitation in the underground supply-beds, and the authorities would be acting wisely by adopting some means of testing the variation of flow in three or four of the best flowing wells. There is no cause for alarm as to the water-supply being insufficient for public requirements, but it is only by carefully recording changes in supply, particularly during or following years of rain-shortage, that a proper estimate can be made as to whether it is advisable to regulate the flow of wells during a portion of the year.

The well owned by the South British Insurance Company to the left of the road after crossing the Tutaekuri bridge on the Taradale Road was put down in 1891 by Mr. Gilberd. It is 133 ft. deep. To the west and south-west of Napier South, in the direction of Greenmeadows and Taradale, the wells die out as the hills are approached. In the year 1890 the late Mr. Tiffen had a well put down near where Mr. Hindmarsh resides at Greenmeadows, to a depth exceeding 600 ft., but without success. The wells in that district vary in depth from 80 ft. to 115 ft. according to position, shallowing towards the hills. The Taradale wells vary from 50 ft. to 95 ft., although Mr. Halpin reports a 2 in. well put down twenty-five years ago to a depth of 125 ft. with a flow of 4,000 gallons per hour. This suggests the existence of a second water-bearing bed. At the Park racecourse there is a well 135 ft. deep; in Avenue Road the Roman Catholic Seminary supply-well is 110 ft.; and at the police-station the well is 100 ft. In the direction of Jervoiston and Meeanee the wells deepen somewhat. Mr. T. B. Harding, of Jervoiston, reports having a well 92 ft. deep, put down in 1901; but Messrs. Harris, Lynch, and Alvine report wells varying from 150 ft. to 160 ft. Mr. English has a well 180 ft., Mr. P. Parsons one 185 ft., and the Rev. Father Hickson reports one 240 ft. deep, all in the Meeanee district. The latter well is said to have been put down in 1862, but this is clearly a mistake, as the first well put down in Hawke's Bay was carried out by Messrs. Bennett and Lord, who arrived in Hawke's Bay from Christchurch in the year 1866; the depth was 170 ft. The late Mr. George Rymer sent me a letter he had received from Mr. Lord, written from Normanby on the 4th October, 1916, the gist of which is that he and Bennett put down a well in Peacock's paddock in November, 1866, which was a failure. Then a trial was made in Davis's paddock in January, 1867, when water was struck at a depth of 145 ft. They then went to the Mission Station and got water at 175 ft. This also was in January, 1867. The well put down in Napier was on the site of Swan's Brewery, the depth being 212 ft., and the flow very good. I give these three wells prominence because of their historical value. The deepest well in Hastings is Newbiggin's. Put down in 1895, three separate flows were found—namely, at 115 ft.; at 198 ft., whence the flow was equal to that at 115 ft., but the water was much harder; and at 271 ft., when an excellent flow was obtained amounting to 30 gallons per minute. In 1904 the Hastings Borough Council put down a bore to a depth of 607 ft., but without success. Quicksand was encountered at 560 ft. In the Clive Grange and Mangateretere districts the wells vary widely in depth, there being two or more beds yielding good flows of water. Quite a number of wells reach 200 ft.; but Mr. J. Bridgman had a well put down in 1912 to the depth of 153 ft. In the year 1904 Mr. John Davidson had a 2 in. well put down to a depth of 130 ft. from which there was a daily flow exceeding 44,000 gallons. The 6 in. well already referred to, at Riverside, between Farndon and Mangateretere, was put down by Mr. Leipst in 1891. It gives more than half a million gallons a day. The cost of sinking was £47, the well being 147 ft. in depth. The Havelock wells are much deeper than the wells scattered over the plain, and are apparently from a different source of supply. Information as to the character of the water would be of much value. Quantitive and qualitative analysis in the case of a public water-supply should be made

mandatory, and the Havelock authorities would be doing a public service by requiring the Health Officer for the district to test the character of the waters flowing from the wells in the district. This question of the quality of water for household purposes receives little or no attention from the proper authorities, and it is only in times of public danger that the matter of the purity of the water-supply is considered worthy of attention. I think the Public Analyst of each health district should ask for specimens of water here and there, as representing the general supply throughout the several centres of population, and the results should be published with as much regularity by the health authorities as is done in other matters connected with the general health of the community. The well in Havelock near the hotel, at the junction of the five roads, was put down in March, 1892. It has a depth of 325 ft., and when inquiry was last made by me it had a flow of 160 gallons a minute. The well on the late Canon St. Hill's property was put down in June, 1894. The bore is 3 in., the depth 335 ft., and the water rose above the surface between 30 ft. and 35 ft. Mr. M. Hardy's well on the Napier-Pakipaki Road, opposite the Presbyterian Church, was put down in 1893 by Mr. Gilberd. The depth is 403 ft., and the flow of water amounts to 25 gallons per minute. There are numerous other wells in the locality, but all the facts show that the source of supply is not the same as for the wells out in the plain, unless it is that the second and third supply-beds of the plain have been tapped, the first bed supplying water on the plain dying out in the direction of Havelock, Te Mata, &c. Reference will be made later on to the origin of the water-supply and to correspondence bearing on the question. Proceeding through Pukehou and Pakipaki, the wells farther to the west and west by south begin to shallow as the latter place is reached, and the whole district, including the freezing-works of Messrs. Borthwick and Co., represents a shallow water-bearing area. I made a special visit to the Pakipaki district in April, 1916, following an unusually dry summer. Many wells were visited, and much information of public interest and value was gathered. Mr. Moroney, a long-time resident of the district, had two wells on his place, one 85 ft. and the other 90 ft. Both of them ceased for a time as flowing wells during the very dry weather of the dry summer of 1914–15, but they recommenced to flow soon after the first heavy rains. Mr. Humphries, another resident, said that his well, which was 80 ft. deep, ran dry in December of 1914, and he had his tap lowered 18 in., but following the early autumn rains the flow returned to normal. Under ordinary circumstances he found a general difference between the height of the summer and winter flow of about' 3 in. Mr. Brooker, whose house is situated on the Te Aute—Havelock Road, had three wells, of a depth of 84 ft., 84 ft., and 90 ft. respectively. The flow from one of the wells rose at the time of my visit 8 ft. above the surface-level. During the course of conversation I was interested to note a similar remark from each of the gentlemen named as to the effect of the long period of dry weather on the flow, and the supposed cause. Each one remarked that when the Poukawa Lake went down, the wells perceptibly diminished their flow, especially during the daytime. The information supplied concerning the wells at Messrs. Borthwick and Sons' freezing-works, as to the effect of the dry summer on the daily supply, is of great interest and suggestiveness. The wells are within a mile or so of the Pakipaki Railway-station, and the depth varies from 90 ft. to 100 ft. according to

Fig. 1.—St. Hill's well, Havelock North. Mr. Leipst. Depth, 335ft″; bore, 3 in.; flow, 60 gallons per minute. Rises 35 ft. above surface. Fig. 2.—Riverside well, Farndon, Clive. Mr. Gilberd, December, 1891. Depth, 121 ft.; flow, half a million gallons a day. Fig. 3.—Otane well, Te Aute. Mr. Leipst, December, 1914. Depth, 71 ft.; bore, 2 in.; flow, 15 gallons per minute. Fig. 4.—Ruataniwha Plain, well near Ongaonga. Mr. Gilberd, 3rd September, 1892. Depth, 316 ft.; bore, 2 in.; flow, 24,000 gallons daily.

locality. Quite a number of wells have been put down to supply the heavy demands at the works and in the paddocks. The older wells, my informant stated, have altered considerably. They alter immediately after rain. During last season some of the wells ceased to flow. A good shower of rain starts dry wells, and increases the flow of others. All wells are down from 90 ft. to 100 ft. Mr. J. C. Crawley, of Longlands, situated between Pakipaki and Havelock North, stated, “The flow alters in dry weather and immediately after rain.” Mr. Buick, of the same district, reported having two wells, and that, following rain, a change is noticeable in the flow in about two days. Mr. C. Livingstone, another settler in the same district, reported having three wells, and that as the rivers increase in volume the wells flow stronger, reaching maximum strength when the Te Aute Lake is at its highest. Thus all owners of wells in the Pakipaki and Longlands districts report a diminished flow in summer and an increase of flow following rains. In some of the returns from owners of wells reference is made to the occasional deposit of sand, and in several instances to the appearance of small crustaceans in the water. In most of the older wells a diminution of flow is remarked. In the Meeanee district a well throws up sand at intervals, and a little sulphuretted hydrogen is given off from water of wells that have been turned off for any length of time. Following the flow of water in a new well in Munro Street, Napier, it was noticed that if a piece of sacking was placed on the top of the pipe and hit smartly with a mallet the water for a minute afterwards was of milky whiteness. In two cases reference was made to the effect of high and low tide on the flow, one well being near the shore, the other at Havelock. The lack of regular observation and the general intensity of flow seaward may account for the absence of information in this direction. In the case of a diminution of flow following a period of dry weather and of a return to normal conditions following rain, more facts would be welcome, especially in the case of wells extending from Napier to Clive Grange and in the Greenmeadows and Taradale districts. The dry weather naturally lessens the quantity of water flowing from a well during long periods of drought, but it does not follow that a fall of ½ in. of rain could by any manner of means have the result of increasing the flow as the outcome of percolation into the beds. Half an inch of rainfall, following a long season of dry weather, will not affect the subsoil to a depth of 12 in. however porous the beds, nor could it possibly be supposed that 1 in. of rainfall would so affect Poukawa Lake as to produce a marked increase in the flow. There can be no reason to doubt the statement made by so many observers that following a rainfall of ½ in., or of 1 in., or even 2 in., the water shows an increase of flow, but I think it must be set down to the fact that the weight—the increased weight on the surface of the land by the fall of rain—is such that it causes, as in the case of the high tide, an increased squeezing of the porous beds. It is likely that each river flowing across the plain does a share in supplying water to the underlying beds, but not by surface soakage. Water falling as rain on a definite area does not remain on that area unless retained in a basin; and soakage into beds can ensue at the outcrop of beds only. It is inconceivable for rain-water to soak through 100 ft. or more of rock made up of a variety of strata, some impervious even to the passage of water. If we can imagine a score or more leaves of a book so placed one

above the other that the edge of each leaf is separate from the overlying edge of a leaf by, say, ½ in. or more, the difficulty of water poured along the edges of the leaves passing very slowly underneath each leaf disappears. As soon as the leaves are wetted the passage of water is very slow, and a long time will ensue for water to pass the full length of each leaf with the varying pressures and the air difficulties to be overcome. But this is what occurs in beds of rock of different materials. Water may pass across the edges of a score of beds of strata on its way from mountain to sea, but the quantity of water that passes into the beds varies according to the porosity of each bed; and the movement of the water in a bed must of necessity be very slow, by reason of the weight of the overlying pressures. It is in this way that underlying beds as they rest against other rocks at their outcrop receive water-supplies from adjacent beds where springs occur at their outcrop. In other words, the outcrop of some beds where springs occur may lie adjacent to other beds which are totally different in material and situation, and which are so porous as to receive most of the waters flowing from springs connected with an entirely different system of rocks. As for Poukawa Lake being the source of supply for the artesian waters of the Heretaunga Plain, it may be of interest to explain the relationship existing between the lake and the plain. Hawke's Bay, extending from Portland Island on the north to Cape Kidnappers towards the south, is a part of a land area that was destroyed in part and was otherwise fractured at a period of great volcanic and earthquake activity at the close of the Pliocene and opening of the Pleistocene periods of geological history. The great break about Waipukurau with the Hatuma Lake, and the line of fracture through Otane and Opapa with the series of lakes formed, according to Maori tradition, by Tara and his dogs, represent the result of the devastation and changes brought about at that time. Since then the earth-building has gone on apace. Only Hatuma Lake remains, representing a much larger lake, and the valley between the ranges of hills extending from Waipawa to Napier has been mostly filled by the washing from the rivers and hills that have taken place. The creek from Poukawa into the plain represents what was at one time a much larger communication, and there can be no doubt that water from the lake percolates into the artesian waterbearing beds long before they come within the direct limits of the plain. But what is said of Poukawa applies equally to other valleys that carry waters to the sea across the plain; hence it follows that there is percolation going on from the Tutaekuri, Ngaruroro, and the Tukituki Rivers long before they enter the limits of the plain, and these sources of supply slowly provide water that is able to give a regular quantity of artesian water, sufficient, apparently, to meet the full requirements of the district, and equivalent, according to my estimate, to an annual rainfall of 7 in. over the entire area of 80,000 acres. Geologically the Heretaunga Plain is connected with the valley extending from Pakipaki through Opapa, Otane, and Hatuma on to the Ruataniwha Plain, and the following information of wells has been supplied to me by the parties directly concerned. Otane.—Towards the end of the year 1914 Mr. Leipst was engaged in putting down a number of wells for Mr. R. H. Tod, of Brae Mead Farm, Otane. The wells are comparatively shallow, the deepest being 71 ft., and the others varying from 63 ft. to 40 ft., the latter being the shallowest put down. The flow varies somewhat in amount, the greatest being at the

rate of 15 gallons per minute. The water is of good quality, but no analysis has been made so far as I am aware. There is no shingle in these wells, the beds in the deepest being 10 ft. friable clay, 15 ft. soft blue clay, 9 ft. shale, 12 ft. greyish-blue clay, 6 ft. shale, 12 ft. blue clay, and 7 ft. shale, in which bed water was obtained (fig. 3). The wells are in the vicinity of an open well where moa-bones were found during the progress of sinking some years previously. This is evidence to show that the valley-beds have been filled in within the moa period, and followed, or was contemporaneous with, the volcanic and earthquake period which modified the surface-features of the North Island and profoundly affected the whole of the east-coast country. The swamp in the same valley some years ago was found to contain cartloads of unimpaired moa and other bones (vide Hamilton, Trans. N.Z. Inst., vol. 21, p. 311, 1889). It is likely that the great basin in which is situated the Hatuma Lake, beyond Waipukurau, with shingle accumulations in various parts, will supply an abundance of water along the line of rift and adjacent thereto. The valley is a portion of the great fault - rift which extends right away from the Manawatu Gorge to Hawke's Bay, in which deposits have since accumulated that have made possible the supply of artesian wells. Ruataniwha Plain Wells.—On this plain area, which is situated 800 ft. or more above sea-level, and is within the drainage-basin of the Tukituki River, the first well was put down in 1892 by Mr. Gilberd for the late Mr. Rechab Harding (fig. 4). The well is situated north by east of the Ongaonga Township, and is 316 ft. deep. The water rose 16 ft. above the surface, giving a flow in a 3 in. well of 10 gallons per minute. Other wells had been put down in Te Ongaonga for the butter-factory, at depths varying from 78 ft. to 125 ft. In the latter well the water rises to a height of 10 ft. above the surface, and is of excellent quality and ample in quantity. Other wells have been put down, but no definite information is obtainable other than from Mr. H. N. Watson, sheep-farmer, of Fairfield, who has supplied me with very important and interesting data concerning a number of wells which he has had put down. Four wells have been sunk by him up to February, 1916, two of which were failures. The first successful well went to a depth of 390 ft., with a 3 in. pipe. The flow was at the rate of 5 gallons a minute at the surface, or 4 gallons at a height of 5 ft. A Douglas ram, size 4, was fixed in position at the 5 ft. level to supply house requirements. The well appears to undergo curious phases in its flow. Sometimes the quantity of water increases very markedly, and at times the flow changes to the consistency of pea-soup, with abundance of sand. At my suggestion Mr. Watson had the water analysed by the Government Analyst, with the following result: Sodium chloride, 1.20 grains per gallon; sodium bicarbonate, 2.50 grains; calcium bicarbonate, 4.86 grains; magnesium bicarbonate, 1.60 grains; silica, 3.92 grains: total grains, 14.08. In Mr. Watson's letter to me from which the above information is taken the following occurs: “I have no doubt whatever, now, that the well varies its flow according to the rainfall in the Ruahines. About a month ago the water suddenly dropped one day in the tank from a level of a few inches below the house intake-pipe to just above the inflow-pipe from the ram. It remained at about the same level for a month, varying very little from day to day. On 30th June (midwinter) we had 0.19 in. of rain, but the Ongaonga Creek did not flow, and the well did not increase at all. Yesterday, although we had practically no rain and the Ongaonga

Creek has not begun to flow, there is a considerable fresh in the Tukituki, and the water was coming down very thick. It was evidently raining in the mountains, and in the evening a little rain fell here. During the afternoon I looked at the well, and thought that the water in the head-tank was rising. This morning it is overflowing at the overflow-pipe, though the ground here is hardly damp and the Ongaonga not flowing. It seems evident that my well will rise and fall in sympathy with the Tukituki River, which rises in the ranges, and not with the Ongaonga Stream, which rises in the plains.” These observations by Mr. Watson as to the changes of flow in his well are of high value, and give a clue as to the source of supply of water for the artesian wells on the Ruataniwha Plain, into and around which the Tukituki has flowed during the filling-up of the plains. It is of great importance to understand the fact that all the artesian wells found in Hawke's Bay, including Ruataniwha and Otane, are situated within the river-system of the Hawke's Bay District. Between Mr. Watson's home and the Ruahine Mountains there is one vast series of shingle terraces which slope towards the Ruataniwha Plain at a comparatively high angle, and extend from thence onward to the sea near Farndon, both by way of Waipawa and Waipukurau, but also by way of Gwavas and Maraekakaho. The formation or building-up of the Heretaunga and Ruataniwha Plains and the Taupo Plateau is of comparatively recent date, and any facts that will help observers to determine a fair estimate of the time that has gone by since the changes occurred should be kept for future use. The information furnished by those who answered the inquiry in a circular letter relating to the artesian wells in certain localities in this district issued by the Hawke's Bay County Council in 1916 at my request has been summarized, the consensus of opinion being that the wells gradually diminish in flow; that the wells from the shallow beds have not the same strong flow as formerly; that the wet and dry seasons alike affect the wells—the flow increasing in the former and diminishing in the latter; and that high tides increase the height of flow, the difference between high and low water being as much as 3 ft. I understand from Mr. John McDougall that a similar change of flow as between high and low water is noticeable in the artesian wells at the Lower Hutt, where the Borough Council have put down wells to supply the requirements of their town. From what has already been stated it must now be apparent that the falling of rain upon a surface like the Heretaunga or Ruataniwha Plain cannot be used for the supply of deep underground beds in the immediate vicinity of a well. The water within an artesian area or basin is not stored water after the manner of an underground tank, but it is moving water like the flowing water in a river-bed of shingle. The Heretaunga Plain, for example, has a variety of old river-beds that have spread like fans so soon as they reached the growing plain from the higher lands of the back country. Across these fans and through the old valleys water still flows from the outcrop-beds in the back country, and it is this water that runs in the underground channels of long ago, being kept in those channels by beds of clay below them and above them, and that is tapped on its way seaward by an artesian pipe. The water in the underground beds flows from the higher areas of the plain towards the lower areas and into the sea. The slope is varied over the plain because, as already pointed out, the underlying beds represent nothing more than old flowage beds or

streams which spread over the plain as the material was deposited during periods of flooding and growth. The process can be watched even now over the plain in times of flooding. The material found during the process of sinking a well suggests the origin or place from whence the material was carried. There is a difference in the material brought down by the Tukituki compared with what is brought down by the Ngaruroro or the Tutaekuri, for the reason that the sources of the latter rivers are within the limits of the volcanic country, where pumice and lava rocks are somewhat abundant, as is also the bluish-grey clay-sand found in the vicinity of solfatara and puia. It is manifest that this water must come from somewhere outside the immediate vicinity of the water-bearing area, and thus the rainfall of the district is benefited to the extent of the amount mentioned in the early part of this paper. From 1871 to the end of 1920 the average rainfall for the Heretaunga Plain has been 34.266 in., the rainfall for each year being as under:— Annual Rainfall in Napier and Vicinity During the Past Fifty Years. Number of Years. Year. Rainfall in Inches. Number of Years. Year. Rainfall in Inches. Number of Years. Year. Rainfall in Inches. 1 1871 35.89 19 1889 35.76 36 1906 30.15 2 1872 23.94 20 1890 27.61 37 1907 37.65 3 1873 42.38 21 1891 29.75 38 1908 32.11 4 1874 37.94 22 1892 40.63 39 1909 36.86 5 1875 38.26 23 1893 57.73 40 1910 36.12 6 1876 38.39 24 1894 40.10 41 1911 35.29 7 1877 33.45 25 1895 34.07 42 1912 29.41 8 1878 21.00 26 1896 35.90 43 1913 25.41 9 1879 53.14 27 1897 41.38 44 1914 24.56 10 1880 38.40 28 1898 30.79 45 1915 24.56 11 1881 24.14 29 1899 37.57 46 1916 36.84 12 1882 37.01 30 1900 45.36 47 1917 46.33 13 1883 42.12 31 1901 27.77 48 1918 32.27 14 1884 39.76 32 1902 36.48 49 1919 25.13 15 1885 23.42 33 1903 31.42 50 1920 28.52 16 1886 21.67 34 1904 36.45 17 1887 26.24 35 1905 46.67 Average 34.266 18 1888 21.62 During the period there were two years when the annual rainfall exceeded 50 in., nine years when it exceeded 40 in. and was less than 50 in., twenty-one years when it exceeded 30 in. and was less than 40 in., eight years when it exceeded 25 in. and was less than 30 in., and ten years when it was less than 25 in. These facts are of considerable importance, as they illustrate wide contrasts in the annual rainfall throughout the district, and show the importance of water-conservation. Settlers do not give much thought to the importance of rain-conservation, though after all it is the rain that supplies artesian beds with water, and were there no porous beds continuous in origin between the back country and the sea there could be no artesian wells. The drainage of a district stops the amount of soakage that was formerly possible throughout the district. When this country was first settled the areas of swamp lands were extensive. Lakes and swamp lands illustrate places where the land is oversaturated with water—in other words, where the supply of water exceeds evaporation and soakage. In sinking in depressed areas where there are no traces of water the line of

underground drainage (known as the water-table) is sometimes reached. In Napier, and, in fact, over the lower portion of the Napier area, the water-table of salt water is only a few feet from the surface, but this arises from the fact that the outer sea is only separated from the inner lagoon-basin area by a shingle-bed. The height of a water-table depends primarily on the annual rainfall of a district, and it can readily be understood how a diminished rainfall of 10 in. or 20 in. in a year must eventually affect the underground flowage, and bring into operation desiccating conditions that vitally influence underground beds in their porosity and their capacity to hold water. Up to the present time there is no regulation affecting the continuous flow of water from an artesian pipe, but the conditions are coming about that will necessitate the adoption of some form of regulation. Except for necessary supplies, all wells should be turned off to the extent of three-fourths of their flow from 6 o'clock at night to 6 on the following morning, and even in Napier the question of regulating the flowage for the borough supply, especially in summer, should receive the attention of the borough authorities. It is urged that here, as in all other districts where artesian wells are in use, the flow of a well should be regulated, and that a stop-tap should be fixed in all cases so that the flow may be increased or decreased as required. In the case of every borough and township a pressure-gauge should be fixed on two or three of the most powerful wells, separated from each other by not less than a quarter of a mile. Many facts of public use could be gathered if the authorities would agree to work together,* Since this paper was written Mr. Berry, engineer in charge of the Napier Borough waterworks, has kept artesian-well records of pressure and flow over a definite period, and the results show that the flow is markedly influenced by the tides. Further records are being taken to test the flow at definite times—i.e., 6 a.m. and 6 p.m.—without reference to tides, but carefully recording barometric pressure at the times indicated. The results will be available on another occasion. and I do not doubt that the artesian beds underneath the Heretaunga Plain could be preserved for many years by careful attention to the condition of the wells. If it has been deemed necessary to establish a River-conservation Board, surely the need is as great in the matter of water-conservation for domestic use. Under a properly constituted authority a vast amount of information might be collected as to flowage, corrosion of pipes, changes in the pressure, and the changing character of the materials held in solution. These facts could be used to suggest profit and loss in the sources of supply, and the corrosion of pipes, and even as to whether creeps are taking place in overlying beds.