Abstract
After stating the need for precise drought data as the basis for the formulation of sound economic schemes of insurance of stock and crops against losses arising from drought, the author outlines methods by which all the requisite essential data can be derived from lengthy meteorological records :β(I) In precise monthβtoβmonth detail, with regard to all the major droughts of a review period, by means of isodef charts showing equal percentage deficiency, and (2) in general detail for the whole review period, which is limited only by the availability of an adequate supply of reliable continuous meteorological records, by means of isnagdef charts (showing equal aggregate deficiency); these, being few in number, do not involve so much labour as the production and investigation of isodef charts for each month of the period of review.
Three typical isoagdef charts for S.E. Queensland, covering the pyear period 1886β1935, together with sample data used in their preparation, are given in illustration of the method.
It is also pointed out that the statistical data and charts are of material value in selecting reserve agistment areas, or in deciding as to the leasehold or freehold values of pastoral and farming properties in recurrent drought areas.