Before and After Integrated Catchment Management in a Headwater Catchment: Changes in Water Quality

Abstract

Few studies have comprehensively measured the effect on water quality of catchment rehabilitation measures in comparison with baseline conditions. Here we have analyzed water clarity and nutrient concentrations and loads for a 13-year period in a headwater catchment within the western Waikato region, New Zealand. For the first 6 years, the entire catchment was used for hill-country cattle and sheep grazing. An integrated catchment management plan was implemented whereby cattle were excluded from riparian areas, the most degraded land was planted in Pinus radiata, channel banks were planted with poplar trees and the beef cattle enterprise was modified. The removal of cattle from riparian areas without additional riparian planting had a positive and rapid effect on stream water clarity. In contrast, the water clarity decreased in those sub-catchments where livestock was excluded but riparian areas were planted with trees and shrubs. We attribute the decrease in water clarity to a reduction in groundcover vegetation that armors stream banks against preparatory erosion processes. Increases in concentrations of forms of P and N were recorded. These increases were attributed to: (i) the reduction of instream nutrient uptake by macrophytes and periphyton due to increased riparian shading; (ii) uncontrolled growth of a nitrogen fixing weed (gorse) in some parts of the catchment, and (iii) the reduction in the nutrient attenuation capacity of seepage wetlands due to the decrease in their areal coverage in response to afforestation. Our findings highlight the complex nature of the water quality response to catchment rehabilitation measures.

Riparian management: A restoration tool for New Zealand streams

“…; Hughes & Quinn ), while others show complex water quality responses (Smith ; Hughes et al . ; Hughes & Quinn ; Table S1). The design of some studies, where multiple good‐management practices have been combined (e.g.…”

“…However, reduced nutrient uptake by in‐stream plants (Matheson et al . ) can tip the balance towards greater export of dissolved nutrients from shaded reaches (Hughes & Quinn ). Using mosaics of shade and selecting a primary objective are possible solutions to this conundrum (Table ).…”

Assessing the Impact of Wastewater Effluent Diversion on Water Quality

“…Observed changes can also be caused by natural temporal variations [23][24]. The study can be developed by trend analysis before and after the event [14].…”

“…Then one compares the before differences against the after differences [23,25]. To develop data in BACI analysis of variance, ANOVA or nonparametric tests are used depending on data type [14,[22][23]. Based on this method, multiple site experiments are developed along with other more complicated solutions where multivariate analysis of ecological data is used.…”

“…Since the 1970s they were used mostly to evaluate the degree of environmental degradation by humans. Today, they are also used to analyse positive changes in the environment related to limitation of emissions, restoration of water bodies, or integrated catchment management [9,[14][15][16]. Scientific literature presents many methods aimed at the limitation of pollutant discharge into freshwater and marine receiving environments; however, only a few studies have related to evaluating the effectiveness of analysed methods [14], which is why studies on developing methods concerning river restoration are necessary [16].…”