Development of Trigger Levels to Assess Catchment Disturbance on Stream Suspended Sediment Loads in the Magela Creek Catchment,Northern Territory,Australia

Trigger levels for fine suspended sediment (FSS) load in streams are required to identify rainfall-runoff events that have significantly elevated FSS loads, compared with expected background loads, as a result of catchment disturbance. Stream FSS load data collected in the mine-impacted Magela Creek catchment in the wet-dry tropics were used to derive water quality management trigger levels for two approaches – a Before-After-Control-Impact Paired difference design (BACIP) and a regression relationship between observed FSS load and corresponding event discharge characteristics. The results indicate that both the BACIP and regression relationship approaches behave similarly, with similar FSS load events elevated above trigger levels. Notwithstanding this, it is recommended that in order to reliably assess the location and magnitude of a catchment disturbance on FSS load, a combination of BACIP and regression relationship approaches must be adopted. In this study, an event with a FSS load above trigger levels associated with both BACIP and the regression relationship fitted for the downstream site is considered to be significantly elevated as a result of a disturbance within the mine-impacted region. While this technique cannot conclusively determine whether the cause of the disturbance is mine-related or natural (such as fire or bank erosion), it is an efficient statistical method of identifying events that warrant further investigation and management action, if required.     

Book reviews

Theodore G. Th. Pigeaud and P. Voorhoeve. Handschriften aus Indonesien (Bali, Java, und Sumatra), xi, 71 pp., 6 plates. Stuttgart: Franz Steiner Verlag Wiesbaden GmbH, 1985. (Verzeichnis der Orientalischen Handschriften in Deutschland, XXVIII, 2.) DM 64,‐

G. J Knapp, Kruidnagelen en christenen: de Verenigde Oost‐Indische Compagnie en de bevolking van Ambon 1656–1696.xii, 323 pp. Dordrecht: Foris Publications, 1987. (Verhandelingen van het Koninklijk Instituut voor Taal‐, Land ‐en Volkenkunde, 125.) Guilders 35.

Rainer Carle (ed.). Cultures and societies North Sumatra. 514 pp. Berlin; Hamburg: Dietrich Reimer Verlag, 1987. (Veröffentlichungen des Seminars für Indonesische und Südseesprachen der Universität Hamburg, 19.) DM 95.

J. Noorduyn. Bima en Sumbawa: bijdragen tot de geschiedenis van de sultanaten Bima en Sumbawa door A. Ligtvoet en G. P. Rouffaer.xii, 187 pp. Dordrecht: Foris Publications, 1987. (Verhandelingen van net Koninklijk Instituut voor Taal‐, Land‐ en Volkenkunde, 129.) Guilders 30.

Anthony J. Whitten and others. The ecology of Sulawesi. By Anthony J. Whitten, Muslimin Mustafa, Gregory S. Henderson,xxi, 777 pp. Yogyakarta: Gadjah Mada University Press, 1987.

Robert Wessing. The soul of ambiguity: the tiger in Southeast Asia. vi, 148 pp. [Dekalb, Illinois]: Center for Southeast Asian Studies, Northern Illinois University, 1986. (Monograph Series on Southeast Asia, Special Report 24.) (Distributed by Cellar Bookshop, 18090 Wyoming, Detroit, Michigan 48221.)