Probabilistically determining roles of groundwater use in aquacultural fishponds

This work probabilistically determined roles of groundwater use in farmed fishponds in the Pingtung plain, southern Taiwan. According to the standard of water quality for aquaculture, three hydrochemical parameters were considered – manganese, arsenic and ammonium–nitrogen. A minimal utilization ratio (UR) of groundwater was obtained from integrating the hydrochemical parameters diluted with surface water or seawater. Through the integration process, safe groundwater used for aquaculture can be determined effectively. Indicator kriging was adopted to estimate spatial probability distributions of UR. A proper groundwater role – UR < 0.1 (sparsely used), 0.1 ≦ UR < 0.5 (minor), 0.5 ≦ UR < 1 (major) or UR = 1 (completely used) – was gauged based on estimated probabilities. The analyzed results reveal that manganese and ammonium–nitrogen are the key factors influencing on groundwater use for aquaculture in this plain. After making the comparison of surveyed and estimated groundwater URs, this study recommends that groundwater in coastal townships can be sparsely used for elevating temperatures of pond water in winter. Meanwhile, inland townships of groundwater overuse should cultivate fish using surface water instead of groundwater; that is, groundwater plays a minor role in fishponds. Aquaculture industries using the substantial amount of groundwater are merely appropriate for development of few inland townships.