Vulnerability of shallow ground water and drinking-water wells to nitrate in the United States: Model of predicted nitrate concentration in shallow, recently recharged ground water -- Input data set for histosols (gwava-s_hist)

This data set represents the amount of histosols soil taxonomic
order, in percent, in the conterminous United States.

The data set was used as an input data layer for a national
model to predict nitrate concentration in shallow ground water.

Nolan and Hitt (2006) developed two national models to predict
contamination of ground water by nonpoint sources of
nitrate. The nonlinear approach to national-scale Ground-WAter
Vulnerability Assessment (GWAVA) uses components representing
nitrogen (N) sources, transport, and attenuation.

One model (GWAVA-S) predicts nitrate contamination of shallow
(typically less than 5 meters deep), recently recharged ground
water, which may or may not be used for drinking. The other
(GWAVA-DW) predicts ambient nitrate concentration in deeper
supplies used for drinking.

This data set is one of 17 data sets (1 output data set and 16
input data sets) associated with the GWAVA-S model. Full details
of the model development are in Nolan and Hitt (2006).

For inputs to the model, spatial attributes representing 16
nitrogen loading and transport and attenuation factors were
compiled as raster data sets (1-km by 1-km grid cell size) for
the conterminous United States (see table 1).

>Table 1.-- Parameters of nonlinear regression model for nitrate in shallow
> ground water (GWAVA-S) and corresponding input spatial data sets.
> [kg, kilograms; km2, square kilometers.]
>
>Nitrogen Source Factors Data Set Name
> 1 farm fertilizer (kg/hectare) gwava-s_ffer
> 2 confined manure (kg/hectare) gwava-s_conf
> 3 orchards/vineyards (percent) gwava-s_orvi
> 4 population density (people/km2) gwava-s_popd
> 5 cropland/pasture/fallow (percent) gwava-s_crpa
>
>Transport to Aquifer Factors
> 6 water input (km2/cm) gwava-s_wtin
> 7 carbonate rocks (yes/no) gwava-s_crox
> 8 basalt and volcanic rocks (yes/no) gwava-s_vrox
> 9 drainage ditch (km2) gwava-s_ddit
> 10 slope (percent x 1000) gwava-s_slop
> 11 glacial till (yes/no) gwava-s_gtil
> 12 clay sediment (percent x 1000) gwava-s_clay
>
>Attenuation Factors
> 13 fresh surface water withdrawal gwava-s_swus
> for irrigation (megaliters/day)
> 14 irrigation tailwater recovery (km2) gwava-s_twre
> 15 histosol soil type (percent) gwava-s_hist
> 16 wetlands (percent) gwava-s_wetl

"Farm fertilizer" is the average annual nitrogen input from
commercial fertilizer applied to agricultural lands, 1992-2001, in
kilograms per hectare.

"Confined manure" is the average annual nitrogen input from
confined animal manure, 1992 and 1997, in kilograms per
hectare.

"Orchards/vineyards" is the percent of orchards/vineyards land
cover classification.

"Population density" is 1990 block group population density, in
people per square kilometer.

"Cropland/pasture/fallow" is the percent of
cropland/pasture/fallow land cover classifications.

"Water input" is the ratio of the total area of irrigated land
to precipitation, in square kilometers per centimeter.

"Carbonate rocks" is the presence or absence of Valley and Ridge
carbonate rocks.

"Basalt and volcanic rocks" is the presence or absence of basalt
and volcanic rocks.

"Drainage ditch" is the area of National Resources Inventory surface
drainage, field ditch conservation practice, in square kilometers.

"Slope" is the soil surface slope, in percent times 1000.

"Glacial till" is the presence or absence of poorly sorted
glacial till east of the Rocky Mountains.

"Clay sediment" is the amount of clay sediment in the soil, in
percent times 1000.

"Fresh surface water withdrawal for irrigation" is the amount of
fresh surface water withdrawal for irrigation, in megaliters per day.

"Irrigation tailwater recovery" is the area of National
Resources Inventory irrigation system, tailwater recovery
conservation practice, in square kilometers.

"Histosol soil type" is the amount of histosols soil taxonomic
order, in percent.

"Wetlands" is the percent of woody wetlands and emergent
herbaceous wetlands land cover classifications.

Reference cited:

Nolan, B.T. and Hitt, K.J., 2006, Vulnerability of shallow
ground water and drinking-water wells to nitrate in the United
States: Environmental Science and Technology, vol. 40, no. 24,
pages 7834-7840.

本数据集表征美国本土范围内有机土（Histosols）土壤分类单元的占比（以百分比计）。

该数据集曾作为输入数据图层，用于构建预测浅层地下水中硝酸盐浓度的全国性模型。

Nolan与Hitt（2006）开发了两款全国性模型，用以预测非点源硝酸盐对地下水的污染。其中，面向全国尺度的地下水脆弱性评价（Ground-WAter Vulnerability Assessment, GWAVA）非线性方法，整合了氮（N）源、运移与衰减三类表征组分。

其中一款模型（GWAVA-S）用于预测浅层（通常深度小于5米）、近期补给地下水的硝酸盐污染风险，此类地下水可作为饮用水源亦可不作此用；另一款模型（GWAVA-DW）则用于预测可作为饮用水源的深层地下水中的硝酸盐本底浓度。

本数据集为关联GWAVA-S模型的17组数据集之一（含1组输出数据集与16组输入数据集）。该模型开发的完整细节可参见Nolan与Hitt（2006）的研究成果。

针对该模型的输入数据，研究团队针对美国本土范围整合了16项表征氮负荷、运移与衰减因子的空间属性数据，其栅格数据集的网格单元尺寸为1km×1km（详见表1）。

>表1 —— 浅层地下水硝酸盐非线性回归模型（GWAVA-S）参数及对应输入空间数据集
> [单位：kg，千克；km²，平方千米]
>
>氮源因子 数据集名称
> 1 农田化肥（千克/公顷） gwava-s_ffer
> 2 圈养畜禽粪便（千克/公顷） gwava-s_conf
> 3 果园/葡萄园占比（百分比） gwava-s_orvi
> 4 人口密度（人/平方千米） gwava-s_popd
> 5 农田/牧场/休耕地占比（百分比） gwava-s_crpa
>
>运移至含水层因子
> 6 水分输入（平方千米/厘米） gwava-s_wtin
> 7 碳酸盐岩分布（是/否） gwava-s_crox
> 8 玄武岩与火山岩分布（是/否） gwava-s_vrox
> 9 排水沟渠面积（平方千米） gwava-s_ddit
> 10 坡度（百分比×1000） gwava-s_slop
> 11 冰碛物分布（是/否） gwava-s_gtil
> 12 黏土沉积物占比（百分比×1000） gwava-s_clay
>
>衰减因子
> 13 灌溉用新鲜地表水取水量（兆升/日） gwava-s_swus
> 14 灌溉尾水回收面积（平方千米） gwava-s_twre
> 15 有机土（Histosols）土壤类型占比（百分比） gwava-s_hist
> 16 湿地占比（百分比） gwava-s_wetl

“农田化肥”指1992-2001年间施用在农田上的商业化肥年均氮输入量，单位为千克/公顷。

“圈养畜禽粪便”指1992年与1997年的圈养畜禽粪便年均氮输入量，单位为千克/公顷。

“果园/葡萄园”指土地覆盖分类中果园与葡萄园的占比。

“人口密度”指1990年街区组人口密度，单位为人/平方千米。

“农田/牧场/休耕地”指土地覆盖分类中农田、牧场与休耕地的占比。

“水分输入”指灌溉土地总面积与降水量的比值，单位为平方千米/厘米。

“碳酸盐岩分布”指瓦利与里奇碳酸盐岩的分布有无情况。

“玄武岩与火山岩”指玄武岩与火山岩的分布有无情况。

“排水沟渠”指美国国家资源清查（National Resources Inventory）中地表排水、田间沟渠保护措施的面积，单位为平方千米。

“坡度”指土壤表面坡度，以百分比乘以1000计。

“冰碛物”指落基山脉以东分选性差的冰碛物的分布有无情况。

“黏土沉积物”指土壤中黏土沉积物的占比，以百分比乘以1000计。

“灌溉用新鲜地表水取水量”指用于灌溉的新鲜地表水取水量，单位为兆升/日。

“灌溉尾水回收”指美国国家资源清查（National Resources Inventory）中灌溉系统尾水回收保护措施的面积，单位为平方千米。

“有机土（Histosols）土壤类型”指有机土土壤分类单元的占比，以百分比计。

“湿地”指土地覆盖分类中木本湿地与挺水草本湿地的占比。

引用文献：

Nolan, B.T. 与 Hitt, K.J.，2006年，《美国浅层地下水与饮用水井对硝酸盐的脆弱性》，《环境科学与技术》，第40卷，第24期，第7834-7840页。