Destructive Water: Water-Caused Natural Disasters, their Abatement and Control (Proceedings of the Conference held at Anaheim, California, June 1996). IAHS Publ. no. 239, 1997. 275

Accidental pollution simulated system and pollutant traesboundary transport problems for the River Tura

NATALIA N. SHAGALOVA The Russian Research Institute for Complex Utilization and Protection of Water Resources, Mira 23, Ekaterinburg 620049,

Abstract The quality of the River Tura in the state of Tumen (middle Urals and west Siberian region) is often affected by industrial discharges from the neighbouring state of Sverdlovsk, which is located upstream and has a concentration of large-scale metallurgical and machine-building industries. Modelling the transport of pollutants from accidental spills is extremely important for the protection of the environment and drinking water resources downstream. A good model allows one to forecast water quality and to give a warning even before the spill crosses the boundary between the states of Sverdlovsk and Tumen. The algorithms for accidental spill transport cover the period from the onset of a spill to the moment it reaches the border of the state of Tumen. The forecast is based on preliminary information on the spill and on a database for potential spill sources. Transfer functions are used for calculating when the spill will arrive at the boundary and to provided a first estimation of the maximum concentration of the spill there.

INTRODUCTION

The problem of accidental spills as one of the extreme sources of water pollution is very important and common in every country (Clark et al., 1990). The Tura River is 1030 km long and is the largest river in Sverdlovsk state. It has a catchment area of 80 400 km2 and has more than 2.5 million inhabitants. The main tributaries of the Tura are the rivers (603 km long), (556 km), (414 km), and (182 km). The largest part of the Tura flows through the state of Sverdlovsk and has high concentrations of heavy industry along its banks. The lower Tura (258 km) flows through the state of Tumen including its capital city also called Tumen. Tumen is about 80 km downstream from the boundary with the state of Sverdlovsk and uses the river as a drinking water source. Tumen is therefore extremely vulnerable to pollution from spills and reliable forecast of incidents of accidental pollution are very necessary. Travel times for a spill that would affect Tumen are about 3-5 days after an accident. The high concentrations of industry along the banks of the Tura make the threat of accidental spills high. There are 11 hydrochemical observation points in Sverdlovsk state, where sampling for river water quality analyses is undertaken several times a month. This is insufficient for observation of the actual water quality and for cases of accidental pollution. 276 Natalia N. Shagalova

THE TRANSBOUNDARY TRANSPORT PROBLEM

After a spillage event, the body responsible for the accident has an obligation to notify the appropriate organizations and services responsible for water quality monitoring, monitoring spills, remedial action, notification of the public, inter­ regional communication etc. These services in turn must notify the territories downstream about the spill and provide information about the type of pollution that will affect the neighbouring state of Tumen (expected arrival time, type, magnitude and concentration of pollution). A draft agreement has been drawn up on the common use and protection of the quality of transboundary water bodies of the Tura River basin between the states of Sverdlovsk and Tumen, including inter-regional communications and remedial action to be taken in the case on an accidental spill (Tchernyaev et al, 1994). According to this agreement it was decided to install a monitoring station at the boundary between the states of Sverdlovsk and Tumen. This would allow continuous monitoring of water quality and alert the necessary organizations when a spill crosses the boundary. At the present time this agreements is only in draft form and remedial measures are not often implemented. As a result, accidental spills become a problem for those downstream. The main problems for the state of Tumen in the case of an accidental spill are "what, when, and how much" will arrive at the boundary and at the drinking water intakes.

MODELLING SYSTEM FOR ACCIDENTAL SPILLS

In the framework of the draft agreement, the transboundary pollution transport simulation system (BOUNDARY) for accidental spills was developed as a tool for early warning, water supply protection, and for the management of remedial measures. Also, the problems associated with the interface between an off-line application of software for pollution transport simulation and on-line monitoring systems have been investigated in the special case where only one monitoring station is situated at the boundary between the two states (Shagalova et al., 1994a). One of the major problems during the design of this modelling system was the possibility of predicting the fate of a pollutant and its transport in the case when information about a spill is inadequate. As such a situation is likely to occur, a database was set up containing an inventory of all the industrial sites in the Tura catchment which might cause considerable water pollution in the event of an accidental spillage. For each plant a list was drawn up of the substances that would threaten water quality. This database was added to the warning system as well as databases with associated hydraulic, chemical and geographic information. The forecast can now be based on preliminary information about the spill and on data of potential spill sources.

DESCRIPTION OF THE METHOD

The transport of a pollution spill along the reach downstream from the site of the Accidental pollution simulated system for the River Tura 277

spill to the boundary of the region is computed using the method of "transfer functions". This method has been applied often to describe transport properties for complex water systems (Dreiss, 1989). Let px(f) be the function of the spill (i.e. evolution of the pollution concentration with time at the location of the spill). Then at the controlling boundary the concentration will be:

p2{t)=)î{t-t')Pi{f)àf (1)

where the transfer function f can be defined both by a theoretical model and by an analysis of the data from known pollution transport events. Because hydraulic data for a river reach are incomplete and the model we apply has low accuracy, we use the simplest form of the function f which allows us to describe the main transport properties of water bodies: f(0 = 0, t < T

\t-T~ [-(t-T) ,J (2) f(0 ID2 _ exp I D -kT\ t > T Here T is the time of transport of pollution from the location of the spill to the controlled boundary, and k is the decay rate. The value D gives the time extension of the pollution stain. We also introduce the relative extension of the stain: D„+D a-^r (3) where Dn is the duration of the spill. Thus in our model the transport function into an adjacent territory is characterized by two parameters: the time delay T and the relative extension a (Shagalova et al., 1994b).

DISCUSSION

The method discussed in this paper provides an estimate of the fate of an accidental spill when there are incomplete initial and transport data— a situation typical of transboundary transport problems. The method is based on the transfer function technique. An alternative method for modelling pollutant transport is a numerical solution of the advection-dispersion equation which has been well investigated and often used (Gils, 1990; Kummer, 1993). However, detailed flow conditions along the river and initial spill data are required for this method to be applied reliably. If these data are incomplete (either inaccurate or partial) the method becomes less advantageous and the transfer function method is preferable. It allows a great variety of calibration techniques, including the application of a theoretical model or functions based on spill observations. Thus this method has significant flexibility and adjustability for modelling complex water systems. 278 Natalia N. Shagalova

REFERENCES

Clark, R. M., Vicory, A. H. & Goodreich, J. A. (1990) The Ohio River oil spill: a case study. J. Am. Wat. Wks Ass. 3, 39-44. Dreiss, S. J. (1989) Regional scale transport in a karst aquifer. Wat. Resour. Res. 25, 126-134. Gils, J. A. G. van (1990) Modelling of Accidental Spills as a Tool for River Management. Delft Hydraulics Publ. no. 431, The Netherlands. Kummer, S. (1993) Water Supply and Spill Response Management for the Mississippi River Upstream of the Twin Cities. US Army Corps of Engineers, St Paul District. Shagalova, N. N., Shagalov, A. G. & Tretjakov, S. V. (1994a) Water quality modelling for accidental pollution spills as a component of river basin monitoring and management systems. In: Proc. Monitoring Tailor-made (Beekbergen, The Netherlands, September 1994), 328-331. Shagalova, N. N., Shagalov. A. G. & Tretjakov, S. V. (1994b) Transboundary modelling system for accidental pollution spills for the Tura River. Report no. 18 of the Russian Research Inst, for Complex Utilization and Protection of Water Resources, Ekaterinburg, Russia. Tchernyaev, A. M., Prokhorova, N. B., Pozdina, E. A. & Loginova, L. 1. (1994) The draft of the agreement about the common use and protection of transboundary water bodies of the Tura River basin between Russian federation states of Sverdlovsk and Tumen. Final Report Russian Research Inst, for Complex Utilization and Protection of Water Resources, Ekaterinburg, Russia.