Overarching HypoTRAIN research topics

The research within the HypoTRAIN network will:

  1. characterize and quantify hyporheic exchange under transient and heterogeneous hydraulic conditions and develop approaches to integrate local and regional drivers of this exchange;
  2. evaluate if our knowledge on the retardation and transformation of organic matter and nutrients and on the microorganisms involved is valid for organic micropollutants and identify the most relevant processes for micropollutant transformation and retention in the hyporheic zone;
  3. extend the knowledge on the interaction between the various drivers of hyporheic productivity and establish quantitative relations between productivity and hydrodynamics;
  4. develop and establish new model concepts which can be used to describe processes in the hyporheic zone, bridging micro- (cm to dm) to macroscale (km) and making possible the quantification of biogeochemical turnover processes and micropollutant transport, retardation, and transformation in heterogeneous and dynamic pore spaces.

These research topics have been developed from the following central hypotheses:

  • The spatially and temporally transient hydraulic conditions are responsible for the long-term performance of the HZ as an effective natural biogeochemical reactor. The high reaction capacity of the hyporheic zone is maintained by dynamic replenishment of nutrients from the river and/or the groundwater, particulate matter from the river, the wash-out of reaction products, and a continuous turnover and regeneration of microbial, protozoan, and micro-metazoan biomass.
  • The HZ has a high potential for the transformation and degradation of organic pollutants. Its efficiency is based on the structural heterogeneity and large diversity and its dynamics. The high surface area of sedimentary matrix and biofilms in the hyporheic zone provides an efficient retention of micropollutants and is thus crucial for biodegradation, abiotic transformation, and sorption.
  • The multiple and transient gradients within the HZ are a prerequisite for the high diversity of metabolic processes and thus for efficient micropollutant and biogeochemical processing. The reaction capacity of the HZ is enhanced by the coexistence and proximity of oxic and anoxic zones. A successive change in redox conditions along the flow path in the HZ promotes the elimination of a wider range of pollutants than in steady-state or homogeneous systems.

Based on these overall objectives and hypotheses, 16 individual ESR projects have been developed that will contribute to substantially deepen the current knowledge on process interactions in hyporheic zones.

last modified 2015-01-06