**Part 3**

**Water Quality** 

142 Current Issues of Water Management

[31] Asa Gholizadeh, 2011. Apparent Electrical Conductivity and Vis-NIR reflectance for

[32] Amin, MSM, ARM Waleed, and MY Abdullah, 2010. Improving Water Management

Serdang Selangor Malaysia.

City, Indonesia, 18-20 March 2010.

Predicting Paddy Soil Properties and Rice Yield. Unpublished PhD Thesis, UPM

using Virtual Rainfall Stations with Radar Derived Rainfall Data. In Proc. of Intnl. Workshop on Integrated Lowland Development and Management, Palembang

**7** 

*Durban, South Africa* 

**Simulation of Stream** 

Muthukrishnavellaisamy Kumarasamy

**Pollutant Transport with Hyporheic** 

**Exchange for Water Resources Management** 

*School of Civil Engineering Surveying & Construction, University of KwaZulu-Natal,* 

Stream channel irregularities, meandering and hyporheic zones, is commonly seen in many riparian streams. These irregular channel geometries often influence the pollutant transport. The stagnation or dead zones are the pockets of stagnant water or water having very low velocities, which trap pollutants and release them at later time to mainstream flow at a rate that depends upon the concentration gradient of the pollutants between the two domains. The stagnation zones are formed near the concave banks of the stream and behind the irregular sand dunes formed on the bed of the stream. The stagnation zones may also be formed due to irregular stream boundaries and also due to localized channel expansions (Bencala & Walters, 1983). The hyporheic zone is a transition zone between terrestrial and aquatic ecosystems and is regarded as an ecologically important ecotone (Boulton et al., 1998; Edwards, 1998). The term hyporheic is derived from Greek language – hypo, meaning under or beneath, and rheos, meaning a stream (Smith, 2005). A number of definitions for the hyporheic zone exist (Triska et al., 1989; Valett et al., 1997; White, 1993), however, the most common connotations are: it is the zone below and adjacent to a streambed in which water from the open channel gets exchanged with interstitial water in the bed sediments; it is the zone around a stream in which fauna characteristic of the hyporheic zones are distributed and live; it is the zone in which groundwater and surface water mix (Smith, 2005). The physical process, of hyporheic exchanges, as described by many investigators (Stanford and Ward, 1988; Stanford and Ward, 1993; Triska et al., 1989; Valett et al., 1997; Brunke and Gonser, 1997, White, 1993) suggest that significant amounts of water are exchanged between the channel and saturated sediments surrounding the channel. Such exchanges have the potential to cause large changes in stream water chemistry and retard the transport of pollutants. The rates of biogeochemical processes and the types of processes governed by flow hydraulics may be fundamentally different. When the groundwater component is negligible, this is possible if there is a fine silt or clay formation underneath the hyporheic zone, the exchanges between the mainstream flow and the hyporheic zone for such condition shall be similar to the stagnation or dead zone processes, i.e., the stream water that enters the subsurface eventually re-enters the stream at some point downstream. The pollutant transport processes for such circumstances can be regarded as hyporheic

exchange. Fig. 1 represents a stream with hyporheic zone.

**1. Introduction** 
