The derivation of the mathematical models for nutrient transport in deposit-water systems is based upon the mode of physical mass transfer via diffusion and adsorption. The two primary objectives in seeking a simple but valid model of the system are: To obtain a physical system constant, i.e. an 'effective' diffusion coefficient which can be used to estimate the flux of nutrients through the deposit and the depth of penetration; and to examine the rate-limiting step(s) of nutrient transport by modeling the interplay of 'interfacial resistance' and pore diffusion and adsorption. The models described are: Pore diffusion through interstitial water of deposit; interfacial mass transport; diffusion with simultaneous adsorption; and release of nutrients via diffusion. This last model of simultaneous adsorption and diffusion may be most useful in gaining an understanding of nutrient interchange.