North Branch Mahantango Creek

North Branch Mahantango Creek is a tributary of Mahantango Creek in Snyder County, Pennsylvania, in the United States. It is 13.3 mi long and flows through West Perry Township, Perry Township, and Chapman Township. The creek's mouth is at 438 ft above sea level.

The ratio of nitrogen to phosphorus in North Branch Mahantango Creek is 18 to 1. The annual loads of sediment, nitrogen, and phosphorus in the part of the creek that is considered impaired by the Pennsylvania Department of Environmental Protection are 2963043 lb, 32045.85 lb, and 1807.092 lb, respectively. The main rock types in the watershed are shale, interbedded sedimentary rock, carbonate rock, and sandstone. The creek's watershed has an area of approximately 37 square miles.

Course
North Branch Mahantango Creek begins in West Perry Township, Snyder County, on Shade Mountain in Bald Eagle State Forest. It flows south-southeast off Shade Mountain and then turns east and flows in Heister Valley between Chestnut Ridge and Lime Ridge. It receives a number of small and unnamed tributaries from the north and after several miles exits West Perry Township. Upon leaving West Perry Township, the creek enters Perry Township and continues flowing east for a short distance. It then reaches the community of Mount Pleasant Mills and turns southeast. The creek crosses Pennsylvania Route 35 and begins paralleling Pennsylvania Route 104, turning south shortly thereafter. It passes Potato Valley, where an unnamed tributary enters it from the west and then passes Buckwheat Valley (where another unnamed tributary enters it from the west) and the community of Shadle. It continues south, passing the Long Woods and receiving a tributary from Trout Valley. The creek then reaches Aline Creek and the community of Aline. A short distance downstream, it reaches the border between Perry Township and Chapman Township. The creek then flows along the border for a few miles, running parallel to Pennsylvania State Game Lands #194. It then reaches its confluence with Mahantango Creek.

Tributaries
Tributaries of North Branch Mahantango Creek include Aline Creek and a number of unnamed tributaries. Several tributaries are considered impaired according to the Pennsylvania Department of Environmental Protection.

Chemical hydrology
A five square mile area of the watershed of North Branch Mahantango Creek is considered by the Pennsylvania Department of Environmental Protection to be impaired.

The part of the North Branch Mahantango Creek watershed that is impaired has an annual sediment load of 2963043 lb. The nitrogen load in this part of the watershed is 32045.85 lb per year and the annual phosphorus load is 1807.092 lb. The annual sediment load in an unimpaired part of the watershed is 2268306.7 lb. The annual nitrogen load in this part of the watershed is 28812.95 lb and the phosphorus load is 1418.8535 lb per year. The total maximum daily load of sediment in the watershed is 2261234 lb per year and the total maximum daily load of phosphorus is 1414 lb per year.

The largest source of phosphorus in the part of the North Branch Mahantango Creek watershed that is impaired is cropland, which is responsible for loading 1120 lb per year into the creek. Other large sources of phosphorus in this part of the watershed include deciduous forest (316 lb annually), hay and pastures (206 lb per year), and groundwater (130 lb per year). 21 lb of phosphorus per year comes from a quarry, 11 lb per year comes from septic systems, and 2 lb per year comes from mixed forest. A total of 1 lb per year comes from coniferous forests and 0.2 lb per year comes from "low-intensity development".

The largest contributor of nitrogen to the part of North Branch Mahantango Creek that is impaired is groundwater, which contributes 18606 lb per year to it. 8352 lb of nitrogen comes from cropland, 2093 lb comes from hay and pastures, and 2011 lb comes from deciduous forest. 748 lb per year comes from septic systems, 188 lb comes from quarries, 22 lb comes from mixed forest, 12 lb comes from coniferous forest, and 2 lb per year comes from "low-intensity development".

The largest contributor of sediment to the part of North Branch Mahantango Creek that is impaired is cropland, which contributes 2017752 lb per year to it. 604497 lb of sediment comes from deciduous forest, 316361 lb comes from hay and pastures, and 13128 lb comes from "low-intensity development". 10458 lb per year comes from a quarry, 2899 lb comes from mixed forest, 1192 lb comes from coniferous forest.

The ratio of nitrogen to phosphorus in North Branch Mahantango Creek is 18 to 1, making phosphorus a limiting nutrient. There is no point source pollution in the impaired part of the watershed.

Geology, geography, and climate
In the impaired section of the watershed of North Branch Mahantango Creek, 38% of the surface rock is sandstone, 25% is carbonate, 24% is shale, and 12% is interbedded sedimentary rock. In an unimpaired portion of the watershed, 50% of the surface rock is sandstone, 34% is interbedded sedimentary rock, 10% is shale, and 6% is carbonate.

Sandstone lies under the northern part of the North Branch Mahantango Creek watershed's impaired section. South of the sandstone is shale. In the southern part of this section of the watershed, there is interbedded sedimentary rock and carbonate rock. A nearby unimpaired part of the watershed has a similar arrangement of rock.

The Mahantango Formation can be found in the watershed of North Branch Mahantango Creek and is named for the creek.

Most of the North Branch Mahantango Creek watershed is mountainous, with spurs and ridges. Its channel is sinuous and runs through rock formations consisting of limestone, sandstone, and shale.

North Branch Mahantango Creek is a limestone stream.

The annual precipitation in the watershed of North Branch Mahantango Creek is 105.62 cm, although it ranged from 40 to 45 in in the early 1920s. The wettest month is June, when 10.83 cm of precipitation falls. The driest month is February, when 6.25 cm falls. The total annual runoff is 8.1 cm and the annual streamflow is 53.4 cm. Streamflow occurs more in March than in any other month (8.5 cm). The months with the least streamflow are July, August, and September, with 0.6 cm of streamflow each. The creek's temperature is 68 F upstream of Mount Pleasant Mills.

Watershed
The watershed of North Branch Mahantango Creek has an area of approximately 37 square miles. According to the Susquehanna River Basin Commission, the creek's watershed is one of the highest-quality watersheds in the lower Susquehanna River watershed.

The most common land use in the impaired part of the watershed of North Branch Mahantango Creek is deciduous forest, which makes up 55.5% of the area. Cropland makes up 21.1% of this part of the watershed and hay and pastures make up 17.3% of it. 3.7% is mixed forest, and 2.5% is coniferous forest. 0.5% of the land (a quarry) is considered "high-intensity development" by the Pennsylvania Department of Environmental Protection. 0.2% of the land is considered "low-intensity development" by the Pennsylvania Department of Environmental Protection. An unimpaired portion of the creek's watershed includes of 58.5% deciduous forest, 21.1% cropland, 11.9% hay and pasture, 4.2% coniferous forest, and 3.2% mixed forest. The remaining 0.7% of this part of the watershed's area consists of 0.5% "low-intensity development" and 0.2% "high-intensity development".

Nearly all of the northern part of the impaired portion of the watershed of North Branch Mahantango Creek is forested and most of the southern part is agricultural or developed. A nearby unimpaired part of the creek's watershed has the same layout. Both parts of the watershed have wetlands.

The elevation of North Branch Mahantango Creek's mouth is 438 ft above sea level. Its elevation decreases at a rate of 40.2 ft per mile as it flows from its source to its mouth.

History
In the early 1920s, agriculture was the main industry in the watershed of West Branch Mahantango Creek. The creek also powered several small gristmills at this time.

The Aline Covered Bridge was built over North Branch Mahantango Creek in 1884. It is a burr truss bridge that is 67 ft long.

Mahantango Creek's name comes from the Delaware word mahantongo, meaning "where we had plenty to eat".

Biology
North Branch Mahantango Creek is stocked with trout. Moderate numbers of brown trout and some young of the year inhabit it. Herds of livestock can freely access the creek. It lacks a protected riparian buffer.

In his book Trout Unlimited's Guide to Pennsylvania Limestone Streams, A. Joseph Armstrong said that North Branch Mahantango Creek "doesn't rival the Little Lehigh or Fishing Creek, but it is an honest-to-goodness limestone stream" and that it "is not an important stream, but in this relatively barren part of the Commonwealth it is worth keeping in mind if you can't fish elsewhere."