Means of collecting Water on the driest Parts of the Island, and Observations on the Advantages resulting from this Practice.
IN the year 1809, 1 made an attempt to introduce the Indian mode of forming tanks, or reservoirs, by means of a mound or embankment. It seemed very practicable ; but the soil not being sufficiently tenacious for retaining water, the first trial did not succeed ; a second, however, was completely successful, and affords a positive demonstration of the practicability of retaining water, collected during the rains, in even the most barren and driest parts of the island.
This had long been a desideratum at St. Helena ; and as nothing tends more to general improvement of a country than the introduction of water in those places, capable of cultivation, which are destitute of natural supplies of this element, I shall here give an account of the successful method which has been carried into effect ; and which already has rendered a considerable portion of land fit for habitation and other useful purposes ; which, before the formation of the reservoir, had always been considered as barren and unprofitable. This reservoir was originally intended for the supply of the soldiers composing the garrison of Ladder Hill ; who, ever since a military post was established there, had been stinted in the supply of water, on account of the laborious task allotted them of bringing it in kegs from James' Town. To relieve them front this fatigue, and to furnish an adequate supply, a tank has been formed on the south side of High Knoll, which, by means of small channels cut on this hill, as well as on the adjoining hill, called "Merrimans," will receive the whole of the rains that fall on a space of several acres. As those hills are mostly covered with grass, the rain water which runs from their declivities, is much cleaner than that from the more level surface of Ladder Hill ; where, for want of vegetation, the soil is readily loosened, and carried off by the streams ; which are, at all times, extremely muddy.
The tank, or reservoir, has been excavated in stiff clay, at the distance of 2800 yards from the new fortifications on Ladder Hill. The prevailing south-east wind, coming down a valley immediately beyond it, keeps the water in constant agitation, and prevents it becoming stagnant or muddy. As the descent from the tank to the fortifications is one foot in ten, the stream moves quickly. A cut stone water course has been laid the whole of the distance. At those places where the ground is tolerably even, it is raised about six inches above the surface. The small ravines, or gullies, are crossed by walls, having openings or gutters for the free passage of the rain, under the water course, so as to pre-vent the muddy water from Ladder Hill, mixing with the purer stream from the tank. The reservoir contains about 4000 tons ; and as it may be expected to be filled twice a year, (during the two rainy seasons) the total annual supply will be about 8000 tons. Allowing 10 tons a day for Ladder Hill, there would re-main 4 or 5000 tons for any intermediate gardens ; or for cottages that may hereafter be erected between High Knoll and Ladder Hill. The whole of Ladder Hill, comprising about 300 acres, has ever been devoid of water, and of no value whatever ; but as a few small cisterns at proper distances can be established near the choicest spots of land, they may possibly invite persons to build and to cultivate. It seems to me that the culture of the melon, pumpkin, grape, and all sorts of esculents, might be carried on extensively ; not by the costly mode of breaking up a great part of the land, and clearing it of rocks and stones, but merely by digging holes two or three feet in diameter, and filling them with good mould and manure. This method, with occasional watering, and particularly in situations sheltered from the south-east wind, would promote the growth of many sorts of vegetables ; and by thus having, water, passing through this, at present desert tract, there might be many places selected, suitable to the purposes of cultivation, and of rearing hogs, poultry, &c.
To form some idea of the immense quantities of pumpkins that might be raised in the manner I have suggested, and which would not only be a valuable acquisition to shipping, but a cheap food for bogs, it will be sufficient to state, that from a dry bank at Plantation-house, of light soil, measuring 360 feet by 12, in which holes were dug, and a few seeds sown in October, 1810, there was, from the first crop, a return of 3,583 pounds of excellent pumpkins : several of which weighed 70 pounds each. I have been informed that this produce is even inferior to that which has been obtained in other places of this island.