Porcupine Lake is a 280 hectare water-body located in the Township of Whitney, with a combined drainage area of 87 km².

It receives inflow from the Upper Porcupine River as well as Bob’s Creek, which drains Bob’s Lake located northeast of Porcupine Lake.

With a flat topography, the maximum depth of Porcupine Lake is 5 meters. This shallow depth results in no thermal stratification and an ortho grade dissolved oxygen profile.

The bottom of the lake is composed of sandy-clay and clay-silt. The Porcupine River begins at Porcupine Lake at an elevation of 277 m and flows northeast under Ontario Highway 101 out of the lake at the community of Porcupine. It continues to flow northeast where it joins with the left tributary, the North Porcupine River. It then flows southeast through the Township of Hoyle and again under Ontario Highway 101 where it reaches its mouth at the northwest corner of Night Hawk Lake at an elevation of 247 m.

The length of the Porcupine River from its outlet at the northeast end of Porcupine Lake to its mouth at Night Hawk Lake is approximately 35 km in total. The North Porcupine River tributary originates at Bigwater Lake and flows eastward for approximately 25 km to its confluence with the Porcupine River.

Bell Creek enters the North Porcupine River from the south and is a major tributary.

Bigwater Lake and the portion of the North Porcupine River located upstream of Bell Creek have been considered representative of background quality as there is little development and no mining activity in the area.

The south branch of the Porcupine River originates as drainage from the area northwest of Three Nations Lake.

Three Nations Lake is a small 57 ha head water lake with no major in flowing streams or tributaries. The primary outflow at the north end, known as Three Nations Creek, flows approximately 6 km to its junction with the main branch of the Porcupine River. Three Nations Creek was altered by the Pamour Mine Pit Expansion. The expansion drained and excavated 14 ha of the Three Nations Lake north basin. This resulted in an indirect alteration of approximately 2.5 km of the headwaters of Three Nations Creek due to diversion of flows. The lake replacement basin is located adjacent to the southeastern side of Three Nations Lake. The realignment of the Three Nations Creek drains Three Nations Lake including this replacement basin and reinstates the lake outlet flow to tie into the existing Three Nations Creek system at a point 4.6 kilometers downstream.