To George Langridge   21 March 1881

Melbourne,

21 March 1881.

To the honorable G. D. Langridge, M.L.A.,

Minister of public works

Sir,

In compliance with your request I had the honor to accompany Mr Le Cren, the Secretary, to the Yan-Yean¹ on the 19th instant, with a view of advising, whether by cultural operations around the Lake and on any of its drainage-areas the Yan-Yean water could be kept freer of such impurities, as very recently were found to deteriorate more or less the water, supplied to the city and its vicinity. In inspecting the Reservoirs at Preston and at the place, where the open aqueduct is connected with the main-pipes, and in proceeding for further inspection to the Yan-Yean Lake and its surroundings, we found the surface of the water in several spots both in the reservoirs and Lake covered by some green scum, drifted together by the wind or current. This film, which is of algic growth, consisting mainly of short spiral coils of a species of Spirillum, allied to the European S. volutans in the group of Oscillariae, and to a slight degree also visible as floating in the deeper parts of the Lake, did not occur in particular copiousness (so I am informed) anywhere in the Yan-Yean during former years; still the water of the Lake itself was at the time of our visit not to any appreciable degree turbid or badly odorous. Whether to the development of this scum and its subsequent decomposition, (especially when as debris blown together) the unpleasant odor and taste, noticed lately in the supply-water of Melbourne, is to any extent attributable, can only be ascertained by further extended observations. Under any circumstance it seems desirable to adopt some simple and inexpensive contrivance to skim off this scum, when largely drifted together and especially when copiously interspersed (as we found it in one of the reservoirs) with decaying larvae of small insects, before in stormy weather the particles of the film may become dispersed again and be drawn off in the supply-pipes, with the possibility of undergoing decay-fermentation on the long way of the water to the city, especially during hot weather. But whatever the direct cause or causes of the deterioration of the Yan-Yean may be, there can be no doubt, that the increasing influx of decaying particles of vegetable growth and of organic egesta into the Lake should be checked by all available means; but here the difficulty is encountered, that more than half of the Land, surrounding the Lake, is held by private proprietors since the early period of our colony, and as this land is utilized for grazing purposes and only a very narrow strip of Governments Ground separates the pastures from the brink of the Yan-Yean, the drainage from the nearest grazing ground into the Lake is likely to become more and more contaminated, indeed even at present sheep-droppings being found washed down to the very edge of the Lake. Moreover the flats, hitherto used as town-common at Whittlesea and as drover's resting-places near Jack's Creek, send their swampy waters with much of impurities also into the Lake after very heavy showers, while operations for obtaining by Government's licences timber from the slopes of the Plenty-Ranges, even where facing the Yan-Yean, are apt to tear up the soil within the drainage area and to contribute additional impurities to the feeders of the Yan Yean, irrespective of the contaminations arising on many farms along the River Plenty above the Lake, pasture-animals of all sorts approaching there without restriction any portion of the very stream, which has been chosen to supply the city and suburbs with water for domestic purposes. I am aware, that turbid flood-water is not admitted into the Yan-Yean Lake, but turned off at the byewash; yet the water even after settling cannot possibly be of the limpid purity, in which it arose at the springs and in which it meandered as rivulets and brooks originally into the Plenty-River, when now it has to pass through so much farm-land. All this, to be contended with, has been pointed out by the officers of the Water-Department; and I merely allude to these difficulties here once more in connection to planting-measures, on which my opinion is especially desired, for the amelioration of the Yan-Yean Water by such means.

If any rearings of plants on the banks below high-water-mark were to be effected, it could be only with such, as will submit to occasional and even lengthened submersion without decay; mainly silicious-coated rushes and sedges would suffer this; but even these, when withering in the annual decay of their stems or when dried up by the lowness of the Lake, may become obnoxious; indeed as a rule the growth of miscellaneous plants between variable high- and low-water mark should be avoided as apt to give rise to putrid fermentation. Actual water-plants again ought to be kept out of Lakes and Reservoirs intended for drinking and cooking water, as small fragments of such aquatic vegetation — ever torn off — would be sure to enter the supply-pipes. One of the best plants, for holding its ground on the banks, would here be the hollow-rush (Heleocharis sphacelata), which occurs as indigenous on a few favorable places on the margin of the Lake and could readily be transferred, if that be found desirable. But I doubt very much, whether the extensive rearing of any rushy plants would much impede the ingress of impurities into the Lake. I would rather recommend, that in first instance a narrow belt of vigorous vegetation be established across the two northern vallies, vize Bear's flat and Back- or Dry-Creek, through which much of the drainage, flowing directly into the Lake, has to pass. The larger and stronger kinds of perennial grasses, fit for humid soil, might readily be sown on a strip of ploughed ground across the above mentioned depressions and on other portions of the surroundings of the Yan-Yean, while the Silt-grass, (Paspalum distichum) might be established in more frequently inundated ground, plants for the purpose being available at the banks of the Yarra, established there from the botanic garden long ago. In percolating through such a dense grassy vegetation, the drainage from the pastures would be freed to a considerable extent of adherent impurities either mechanically or by absorption and chemical changes; but a still more powerful barrier might be set to the flowing of any contaminating matter into the Yan-Yean, if a belt of the tall Donax-reed and of the several kinds of Bamboos, early introduced into the colony, was likewise planted over the ground of the principal drainage near the Lake, whereby moreover the lacustrine landscape would become more embellished; and as the Yan-Yean will always be here a favorite place for rural pleasure-parties, its scenic ornamentation might be still further enhanced with every advantage to the Lake itself by the ready raising of masses of our tall Gippsland Fan-Palm, of Date-Palms and other hardy species of that noble order of plants. Whether means could be devised readily, to filter any water of the Plenty-River through sand, before it enters the Lake, as is done with the water of the River Elbe for the supply of the City of Hamburg, is beyond the scope of this special report.

In reference to your request, to be informed, what kinds of trees ought to be chosen for plantations on the Whittlesea-flat, I would submit, that the choice should be largely of such kinds, as would render their culture finally one of permanent remunerativeness in a commercial point of view, unless it is merely desired, to plant quick-growing trees, such as Eucalypts, Willows, Poplars &c for the absorption of of² humidity. The European Walnut-tree and the North-American congeners as well as the best of Hickories would remain lasting for the yield of their nuts, the Cork-Oak for its bark, the Valonia-Oak for its tan-acorns, the Sugar-Maple for its sap. According to the wetter or drier ground of the reserve many kinds of Pines could be chosen, especially such as can be tapped for turpentine, as the Scotch Fir, the Pinaster, the Haleppo-Pine³ and from the United states the Southern Swamp-Pine, the Pitch-Pine, the Frankincence-Pine, the Lambertian Fir, besides several from the higher mountain-regions of India. Some of the best Nut-Pines could also be grown to advantage, especially the American sorts. In the wettest places the gigantic Virginian Swamp-Cypress could be reared. All these kinds of trees were brought experimentally to Victoria already many years ago. Under any circumstances it would be advisable, to have a large interspersion of Conifers into the intended tree-plantation, in as much as the decaying leaves of most deciduous trees, when occasionally flooded into the Lake, might impair by their decomposition the purity of the water, whereas the tardily falling foliage of Pines on account of its antiseptic oil will not impart any unpleasant odor or taste to water. As the drainage of Whittlesea-flat finds now and then an outlet to the Yan-Yean, it would not be recommendable, to cause at any future time a heavy traffic on it by the rearing of trees solely for timber; but so favorable an area might partly be devoted without any very heavy expenditure to a general Arboretum for the local test-growth of a great variety of trees and perhaps even of a host of utilitarian shrubs, and might thus become a nucleus for forest-culture in the Yan-Yean region for the ultimate benefit of the extensive lands, there permanently reserved by the Government.

In conclusion I may be permitted to express a hope, that the metropolitan and suburban communities will cooperate with the Government more generally in providing tanks for the storage of rain-water, than has hitherto been done. For altho' the magnificent Yan-Yean works yield under ordinary circumstances a more copious supply of water of fair quality, than many other cities and towns elsewhere enjoy, yet no water of any aqueducts of great length and supplied from a vast drainage area can possibly compete in purity with rain-water, collected from well-kept roofs. If therefore each household would only provide for itself a tank (or in high-lying grounds perhaps a cistern) the purest of drinking and cooking water would become everywhere independently available, the demands on the Yan-Yean for general purposes in days of excessive heat would become lessened, and an enormous addition to the water-supply of the metropolis and adjoining cities would be gained from thousands of roofs thus for now unutilized.

I have the honor to be, Sir,

your obedient servant

Ferd. von Mueller.

Heleocharis sphacelata

Oscillariae

Paspalum distichum

Spirillum volutans