Wallumbilla agricultural catchment study 1982-2000 (Queensland, Australia)

A catchment study was established in 1983 on one of the major soil types (a brigalow brown clay) of the western Darling Downs. The objective of this 18 year duration study was to explore changes in soil water, catchment hydrology and water quality associated with different soil surface conditions i.e. tillage, stubble management, gypsum, roughness. The site was chosen to represent clay soils with high water holding capacity in the Maranoa region, where fallowing to store water for later crop growth is an essential risk management tool.
Rainfall, soil water, runoff, suspended sediment concentration, cover and all agronomic operations were monitored on four contour bay catchments. Different tillage practices and a pasture were used to create a range of soil cover and roughness conditions in order to explore functional relationships between land management, soil conditions, hydrology and water quality. This study aimed to compliment similar studies at Greenmount and Greenwood on the eastern Darling Downs.
This dataset provides benchmark data for further hydrologic and water quality studies.

Key findings
Daily runoff was determined strongly by soil water content which was strongly influenced by antecedent rainfall, water use and evaporation patterns. Surface cover and roughness had subtle influences on runoff, and a greater effect on suspended sediment concentrations. Runoff and suspended sediment movement was considerably lower under pasture than cropping.
Accumulation of soil water in fallows was inefficient, with fallow efficiencies ranging from -7 to 40% due to high evaporation and runoff losses.
Runoff and sediment concentration were both inversely related to surface cover and total soil movement was greatly reduced by surface cover. Greater than 75% of the variance in soil movement from single events was explained by surface cover and peak runoff rate.
Differences in hydrology and water quality associated with different management (tillage) were more subtle than experienced on two similar sites on the eastern Darling Downs (Greenmount and Greenwood), mainly due to the lower levels of stubble available after winter crops due to the drier climate. Tillage (roughness) was equally influential as cover on runoff.

1983年，研究人员在达令唐斯西部（western Darling Downs）的主要土壤类型之一——布里格洛棕粘土（brigalow brown clay）区域建立了流域研究（catchment study）。这项为期18年的研究旨在探究不同土壤表层条件（即耕作（tillage）、秸秆管理（stubble management）、石膏（gypsum）施用、地表粗糙度（roughness））下的土壤水分（soil water）、流域水文（catchment hydrology）及水质（water quality）变化。该站点被选为代表马拉诺阿地区（Maranoa region）高持水性粘壤土的典型样区，在该区域，通过休耕（fallowing）储存水分以供后续作物生长是一项重要的风险管理手段。

研究对4个等高带流域（contour bay catchments）的降雨、土壤水分、径流（runoff）、悬浮泥沙浓度（suspended sediment concentration）、地表覆盖度（surface cover）及所有农艺操作（agronomic operations）进行了全程监测。通过采用差异化耕作措施（tillage practices）与牧草种植（pasture）模式，构建了一系列地表覆盖度与粗糙度梯度条件，以系统探究土地管理（land management）、土壤状况、水文过程与水质之间的函数关联（functional relationships）。本研究旨在补充达令唐斯东部格林蒙特（Greenmount）与格林伍德（Greenwood）开展的同类研究工作。

本数据集可为后续水文与水质相关研究提供基准数据（benchmark data）。

## 主要研究发现
日径流量（Daily runoff）主要由土壤含水量（soil water content）决定，而土壤含水量又受前期降雨（antecedent rainfall）、作物水分消耗及蒸发模式（evaporation patterns）的显著调控。地表覆盖度与地表粗糙度对径流量的影响相对微弱，但对悬浮泥沙浓度的调控作用更为显著。牧草种植模式下的径流与悬浮泥沙输移（sediment movement）量远低于作物种植（cropping）模式。

休耕阶段的土壤水分蓄积效率偏低，受高强度蒸发与径流损失影响，休耕效率（fallow efficiencies）介于-7%至40%之间。

径流与泥沙浓度（sediment concentration）均与地表覆盖度呈负相关关系，地表覆盖度可显著降低土壤总迁移（soil movement）量。单次侵蚀事件中，75%以上的土壤迁移量变异可由地表覆盖度与峰值径流量（peak runoff rate）解释。

与不同耕作管理措施相关的水文与水质差异，较达令唐斯东部两个类似站点（格林蒙特与格林伍德）的观测结果更为微弱，这主要源于区域气候更干燥，冬作物收获后残留秸秆量更低。耕作措施（地表粗糙度）对径流量的影响与地表覆盖度相当。