Nolan River is a river in north central Texas, running through Johnson County and Hill County and is part of the Brazos River drainage basin. The Nolan's headwaters are in farm land in northwest Johnson County. The river runs generally parallel to, and about 10 miles east of, the Brazos River. The Nolan flows in a southeasterly direction from its headwate…Nolan River is a river in north central Texas, running through Johnson County and Hill County and is part of the Brazos River drainage basin. The Nolan's headwaters are in farm land in northwest Johnson County. The river runs generally parallel to, and about 10 miles east of, the Brazos River. The Nolan flows in a southeasterly direction from its headwaters for about 27 miles to its confluence with the Brazos River in the headwaters of Lake Whitney in Hill County, south of the town of Blum, Texas.