The Örtze rises north of Munster in the Große Heide (in the Raubkammer federal forest) and, after 62 kilometres (39 mi), joins the Aller southeast of Winsen.

It was formed during the Saale glaciation about 230,000 to 130,000 years ago by the drainage of meltwater from the ice sheet which cut 20 to 50 metres (65 to 165 ft) deep into the plateaus of the southern Lüneburg Heath.

In order to remove suspended solids and sediments which are washed away during heavy rains from the tank training areas with their sparse covering of vegetation, four successive lakes – the so-called Munoseen – have been created on the Örtze, and, on the Ilster, the main headstream of the river, there is a further dam pond.

The Örtze is the largest river on the Southern Heath or Südheide and drains its central area, between the rather longer Böhme to the west and the Ise to the east.

Before it was renaturalised its upper course acted as a drainage ditch for the former raised bog, now afforrested, in the narrow valley (nature reserve).

[2] On the headstreams of the Landwehrbach lies the Faßberg Air Base (north of Schmarbeck) and numerous old kieselgur pits (either side of the Sothrieth).

[3][4] Alders, pines and spruce along the river bank provide shade, keeping the water cool even in summer and the oxygen content high.

The fish and animal species found in the river include: freshwater eels (Anguilla anguilla) and burbots (Lota lota), grayling (Thymallus thymallus), brown trout (Salmo trutta forma fario), bream (Abramis brama), minnow (Phoxinus phoxinus), perch (Perca fluviatilis), Gudgeon (Gobio gobio), pike (Esox lucius), bullhead (Cottus gobio), roach (Leuciscus rutilus), rudd (Scardinius erytrophthalmus) and brook lamprey (Lampreta planeri).

She is so modest, so wise and so still, like a real child of the heath; it would be an easy thing for her if she went her own way to the sea, because even in the driest summer she has enough water, the brooks and streams from the moors, the Schmarbeck and Sotriet, Lutter and Wittbeck, Wietze and Brunau, do not let her go thirsty.

On 28 February 1677 the prince's master rafter (Floßmeister), Johann Bastian Erhardt, looked into the possibility of using the river to float timber downstream from forest in the areas of Hassel, Lüß and Kalbsloh.

Its supply, by contrast, was from private landowners and local communities (Realgemeinden) to whom large areas of old forest had been transferred following the division of common land in the mid-19th century.

In the second half of the 19th century there were also 11 raft-building points from Müden to Oldendorf where the logs hauled to the river by horse and cart were tied together to form a raft.

One feature were the rounded willow hoops at the front, the so-called hand rails (Handregels), which the rafter could grab in an emergency.