Water losses, seasonal mass loading, and best management practices for crawfish ponds

Some crawfish (Procambarus clarkii and P. zonangulus) ponds discharge into impaired water bodies in Louisiana. The objectives of this research were to develop water discharge models, determine seasonal mass loading of solids and nutrients, assess effluent quality during final drawdown (May through June), and identify best management practices for crawfish ponds. Average crawfish pond water loss during a production cycle was 228 cm and was partitioned among evapotranspiration (68%), precipitation overflow (13%), final drawdown (13%), and infiltration (6%). Modeling indicated that 15-cm of water storage capacity reduced precipitation overflow by 28% in high precipitation years, 61% in average precipitation years, and 100% in low precipitation years. Predicted mass loading was greatest in the winter (precipitation overflow) and late spring through early summer (final drawdown). During final drawdown, total suspended solids (TSS) were high in the first 5% and last 20% of water discharged. During final drawdown, deep vegetated ditches provided the best TSS reduction compared to narrow, shallow, non-vegetated ditches. Slow draining from the water surface and avoiding drainage of the final 20% of the pond volume are recommended best management practices. The final 20% of the pond volume can be treated in deep vegetated ditches, settling basins, or constructed wetlands.