『Abstract
The health of near shore marine ecosystems has long been a concern
because of its importance to coastal areas. Jiaozhou Bay (JZB)
is one such marine ecosystem experiencing rapid water quality
degradation in the last several decades. From the area surrounding
the bay, the nutrients discharged into the bay through surface
water and groundwater has been greatly changed. The thickness
of the aquifers and the permeability is relatively high, the concentrations
of nutrients in the groundwater are generally high, and so the
groundwater discharged into JZB is very significant. However,
no attempt has ever been made to evaluate the amount of nutrients
discharged into the bay area via groundwater. In this study, the
cross-section method and water balance method were used to estimate
the amount of groundwater and nutrients discharged into JZB via
the subsurface. Groundwater was monitored and sampled at aquifers
surrounding the bay area, and some previously available data was
also analyzed. The results indicated that groundwater from the
Baisha Aquifer east of JZB now is the major source of nutrients
(nitrate, dissolved SiO2) being discharged
into the bay. The concentrations of nutrients in the groundwater
have been increasing with intensive agricultural land use. However,
Dagu Aquifer, the largest aquifer north of JZB, only provides
limited nutrients to the bay area because of the construction
of a low permeability subsurface dam. Historically, during the
1970s to the 1990s, the Baisha Aquifer experienced seawater intrusion
due to excessive groundwater withdrawal. The same was true for
the Dagu Aquifer from the 1980s to the 1990s. Because of this,
no significant nutrients were discharged into the bay.
Keywords: Groundwater discharge; Nutrients; Cross-section method;
Water balance method; Jiaozhou Bay』
1. Introduction
2. Hydrological setting
3. Groundwater regimes in the sedimentary aquifers
3.1. Dagu Aquifer
3.2. Baisha Aquifer
3.3. Yang Aquifer
4. Methodology
4.1. Sample collection and analysis
4.2. SGD estimation methods
4.2.1. Cross-section method
4.2.2. Water balance method
4.3. Data processing and parameter estimation
5. Results
5.1. SGD from the Dagu Aquifer
5.2. SGD from the Baisha Aquifer
5.3. SGD from the Yang Aquifer
7. Conclusions
Acknowledgments
References