The industrial city of Hama lies on the Nasun. It uses the power of the river to drive its industry via waterwheels. The noria at Hama irrigate many towns further from the river along the road. The fertile band along the Nasun, fed by its annual floods, is the main source of Lenthinar's food.
A nasunometer is located on the isle of Kifi, not far north of Hama.
Most of the population of Lenthinar and all of its cities, with the exception of the new city of Hama and those near the coast, lie along those parts of the Nasun valley south of Hagari; and nearly all the cultural and historical sites of Ancient Lenthinar are found along the banks of the river. The Nasun ends in a large delta that empties into the sea.
Now the Nasun, when it overflows, floods not only the Delta, but also the tracts of country on both sides of the stream, in some places reaching to the extent of two days' journey from its banks. – Herodotus
Flooding of the Nasun is an important cycle in Lenthinar. It is celebrated by Lenthinari as an annual holiday for two weeks starting in mid August, known as Fath El Nasun, the festival of the Opening of the Meryt Canal. The Meryt Canal originates opposite Kifi Island and is blocked with a flood gate. It is opened when the water level in the Nasun River reaches 24 feet deep. At this level, the summer flood from the river is used to fill the canal. During the celebrations, decorated boats crowd the river. Those who have witnessed it refer to it as Hama's most spectacular festival. Near the nasunometer is a temple for prayers. The grand celebration is not a guaranteed annual event. Years when the Nasun flood water fails to reach 24 feet, the celebrations are canceled, and prayers and fasting are held instead.
Every summer, torrential rains in the Hordeland highlands cause a drastic increase in the volume of water flowing into the Nasun from the lakes and its tributaries. Between June and September, the reaches of the Nasun running through Lenthinar burst their banks and cover the adjacent flood plain. When the waters receed, around September or October, they leave behind a rich alluvial deposit of exceptionally fertile black silt over the croplands. The inundation – akhet in the Lenthinari language – was one of the three seasons into which the Ancient Lenthinari divided their years.
The three stages of the Lenthinari flood cycle are Akhet, the time of the Nasun flood, Peret, the sowing time, and Shemu, the time of harvest.
The flood cycle is so predictable that the Ancient Lenthinari even based their calendar on it. Akhet was the first season of the year. Peret or the Lenthinari Autumn season marked the time when crops grew in the fields and were harvested, running from October to mid-February. Shemu was the third and last season of the Lenthinari year which ran from mid-February until the end of May; it essentially signalled the spring season of the Lenthinari calendar. In this season, the river is low and rather dry. Modern Lenthinari still refer to these seasons.
"I will take you as far north as Hagari, but I won't pay the toll. Won't go to Al Philae anyhow. No captain in his right mind would sail to Al Philae in late Shemu, unless he'd rather spend his time stranded on a rock than in his trim boat, with her hull still whole and sound." -- Captain Ankhu
A Khamaseen is a cyclonic type wind that is common in Lenthinar in two seasons of each year: towards the end of March and April (mid Shemu), and between September and November (cusp of Akhet & Peret). Hot weather ensues, as well as sandstorms. It is an oppressive, hot, dusty, west wind occurring intermittently in the Badlands and Lenthinar, especially at night. The wind is said to occur for a total of fifty days per year, and the name is derived from the Lenhinari for 'fifty', khamsun. It is perilous to sail the Nasun during the Khamaseen.
The Khamaseen is also known as a herald of the river receeding. Once the Khamaseen has blown in Shemu, the river has receeded to the point where sailing cataracts is trecherous. During the Khamaseen at the cusp of Akhet & Peret, the river receeds from flood levels back into its banks. From that point until it blows again, there is a steady south wind that boats can use to easily sail up the Nasun, while they use the river flow to ride down. This is the best time to ride the Nasun, and when the most shipping occurs. After the Shemu Khamaseen, there is much less river traffic, and the Lower Canal is closed. At this point, the majority of boat traffic on the Nasun is grain barges, poling up and down the river, as the flow is sluggish, and the winds are unreliable.
During the heaviest surges of Akhet, it is perilous to ride the river, as the power of the flowes is overwhelming, and a sailor never knows where the river will take him when it overflows its banks. In early Akhet, the cataracts are parilous, as they become white water rapids. In late Akhet, boaters watch the tall poles protruding from the water, indicating the bank edges, beyond which a boat could easily stick in a field, a submergerd shed, or some other part of daily life above water. Mid Akhet is easily navigable, and is a shorter season of bustling river trade, when people carefully watch the nasunometers.