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The hydrology of the Loosdrecht lakes area (1992)

Engelen, G. B. ; Kal, B. F. M. ; Buyse, J. J. ; [et al.]

Springer

Hydrobiologia 233 (1992), S. 21-38

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ISSN: 1573-5117

Keywords: lake restoration ; hydrological systems ; nutrient balance ; groundwater modelling ; water management

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract The hydrological research of the Loosdrecht Lakes and their surroundings over the period 1982–1990 was based on the integrated systems approach to surface- and ground water, with respect to their quantity and quality. The description of the water systems includes an evaluation of the structure and interactions of water systems in and around the lakes since the beginning of the Holocene until recent times, focussing progressively from the regional to the local systems and from the lake complex to the individual lakes. Quantitative research concerned: monthly and annual water balances for the complex of lakes and for individual lakes; numerical two- and semi-three-dimensional groundwater flow models; field experiments on turbulence and diffusion; and experimental laboratory studies on wind-driven currents. Qualitative research concerned: behaviour of environmental isotopes in groundwater; heavy metals in lake bottom sediments; phosphorus balances of the complex of lakes and of individual lakes for the existing and the simulated conditions; and remote sensing studies for the water quality pattern recognition. The interaction between the various water systems in the area has been influenced strongly in historic and recent times by human interference on both the local and regional scales of the water resources, e.g. through the reclamation of lakes, the extraction of water for public water supply, the regional transfer of water, the agricultural and urban activities etc. Two major remedial measures have been taken thus far: construction of sewer systems, and the supply with dephosphorized water from the Amsterdam-Rhine canal. These measures resulted in a decrease of the external P-load but did not result in a significant decrease in eutrophication as yet. Scenario's to improve this situation either pertain to tackling the fundamental causes of the eutrophication or to redressing their effects. The first category includes: drastic reductions in groundwater abstraction for public supply in the Gooi catchment area of the lakes and (partial?) flooding of adjacent deep polder areas to reduce the leakage losses from the lakes (both measures aim at restoration of the water balance). The second category involves less drastic water management alternatives for lake restoration: dredging P-enriched bottom sediments; reinforced flushing during summer with dephosphorized Amsterdam-Rhine Canal water; interception and rerouting of polluted inflows from the watershed; or additional P-removal from yet untreated inflows.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00016093

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Monthly mass balances for compartments of the Loosdrecht Lakes system: Approach and preliminary results (1986)

Kal, B. F. M.

Springer

Aquatic ecology 20 (1986), S. 27-39

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ISSN: 1573-5125

Keywords: mass balances ; nutrients ; lake restoration ; hydrology of lakes

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Water quality modelling in the framework of the Water Quality Research Loosdrecht Lakes requires mass balances covering periods of one month or less for at least three of the lake compartments of the Loosdrecht Lakes system: the Loosdrecht Lakes, L. Vuntus and L. Breukeleveen. The hydrological system of the Loosdrecht area underlying these mass balances is described. Data available on the various mass balance items are surveyed, as well as the methods considered to calculate those items that do not lend themselves to direct measurement. The system will be modelled by means of a series of interdependent spreadsheets. Calibration of this model to the 1983–1986 data set should render it suitable to calculate the mass balances retrospectively,i.e. in the period 1975–1982. The model in its present form cannot be used to predict mass balances. Masses of Cl, P and N stored in the three main lake compartments of interest at consecutive sampling dates in 1983 and 1984 are graphically presented and compared with roughly estimated biannual balances of the same substances for the aggregate of the three lake compartments. Not unexpectedly, the distribution within the system of the conservative substance Cl is a function of the differences between the lake compartments in mixing ratios of high-Cl to low-Cl inputs. The amounts of the nutrients P and N stored in the lake water follow a rather erratic course. Though it is possible to idealize this to a seasonal cycle, the two-year period dealt with by this study is too short to identify such a cycle with certainty. From the large residual terms of the biannual nutrient balances it is obvious that the not directly quantifiable processes like sedimentation, release from the sediment and (presumably) denitrification that are lumped into those residual terms, are of major importance to the amounts of nutrients in the lake water.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02291148

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