Reliability Issue in Projections of the Impacts of Climate Change and Other Changes on Water Resources - page 01

Observed Hydrological Changes

Before talking about the issue of this paper – the question of reliability in hydrological projections, let's take a look to the observed hydrological changes on four major domestic rivers in Serbia (Figure 1). The period 1949-2006 was convenient because it was relatively long (58 years), data were available from numerous monitoring stations, and this period exhibited a close similarity to estimated long-term river discharge trends in Serbia. Eighteen selected river monitoring stations in Serbia, for this period, observed discharge trends indicating that the average yearly hydrological trend in Serbia is approximately -30%/100 years, but its spatial distribution varies (Institute Jaroslav Černi 2012, Dimkić et al. 2013, SEPA 2014).

What Changes a Water Resource?

Apart from climate change (CC), the hydrologic regime of a river is affected by changes in land use (LU) within the catchment area, and changes in the extent and method of human use (HU) of water (Gavrilović Z. et al. 2013, Nachtnebel H.P. 2013, Vasiljević B. et al. 2013). As a result, some of Serbia's rivers record a considerable decrease in discharge. The discharges of only a small number of rivers have increased, largely due to water transfers from other river basins, which began in the 1970's and 1980's.


Figure 1: Graphs showing the observed hydrological changes on four major domestic rivers in Serbia.


Most of the recent projects are based on different climate models and different scenarios that provide basic inputs for hydrological models. Some of the outcomes (on an annual basis) of these projects are summarized in Table 1. A large number of studies based on regional climate-hydrological models address only the first type of change (CC).



This paper neither reports nor considers the outcomes of these projects which relate to the various seasons of the year or extreme high or low flows.