Climate. – Just as geognostic characters and superficial forms differ when they descend from the most internal and elevated parts of the country to the sea, so do the characteristics of the climate, albeit on a small scale. In truth, all of Belgium participates, like other Western European countries, in the characteristics of the oceanic climate (made even more sensitive by the very strong predominance of the SW and W sea winds): moderate seasonal variation in temperatures, copious humidity, frequent rains and storms, sky almost always wrapped in light veils or mist; but there are considerable differences between part and part of the country in relation to the different altitudes and to the shorter or greater distance from the sea. Compare, for example, the minimum averages for January and the maximum averages for July for three locations: Ostend on the North Sea (7 m.) -0.9, +20.7, Uccle (Brussels, 100 m.) −0.8, 22.4, Carlsbourg (Ardennes, 396 m.) -2.9, +21. Another long series of averages shows in Ostend the first day of frost on 16 November, the last on 23 March, in Brussels respectively on 10 November and 4 April, in Bastogne (Ardennes, 503 m.) On 5 October and 11 May. In Eastogne, in the Hautes Fagnes, the days of frost are 145 on average each year, and the cold is in the whole district made more painful by the long duration of the snow and by the violence of the winds. As for rainfall, the average amount along the coast amounts to just over 800 mm., In the inland plains from 700 to 800, then, the relief is accentuated, beyond Meuse, with a rapid progression from 800 to 1000, finally on the maximum heights of the Ardennes around 1500. The average number of rainy days for the country as a whole is 198. The rainfall is abundant in each month; season of maximum rainfall in autumn, but with an already noticeable number of summers; in fact, the most abundant months of rain are October and August.
In relation to these characteristics of the climate it should be noted that in the coastal cultivated area it is generally not possible to harvest, due to moderate heat, before 15 August, whereas in the Flemish lowland the already sensitive heat allows the harvest ten days earlier; on the other hand, for the more favorable winter temperatures, the coastal plain offers a better hotel than the villages inside the plants that fear the cold the most and that could less resist prolonged frosts in the middle of spring.
Hydrography. – Belgium’s irrigation waters are all collected in the two basins of the Scheldt and the Meuse, as well as in the small coastal basin of the Yser. However, none of these three rivers have their entire course in Belgium: the Yser runs through the country for 50 km. out of 73, the Scheldt for 233 out of 430, the Meuse for 183 out of 925, all three with the highest course in France, and Schelde and Meuse with the lowest course in Holland. Thus these rivers like their tributaries have certain common characters reflecting the common climatic conditions; that is, they derive their nourishment for the most part from the rains, large of their tribute in every season of the year; they are therefore regular rivers, unless this regularity is disturbed by the particular conditions of the soils of the basin.
The Yser is a very regular river, very short but flowing with rich waters in a flat plain, therefore easily channeled, together with the small tributaries, to the mouth. It owes the rich waters, as well as the many precipitations, to the impermeability of the clayey surface. For Belgium 1996, please check pharmacylib.com.
The Schelda (fr. Escaut) is also a regular river, which however, given its course on impermeable ground and the slowness of the outflow caused by the very low slope, can sometimes increase its volume dangerously due to an exceptional rainfall. Although French for a quarter of the course and Dutch in the whole lower part, the Schelde is truly the Belgian river par excellence, draining it with its waters, entirely channeled, and with those of its tributaries, the whole central part – almost half – of the whole country. From the Lys, which represents the westernmost tributary, to the Demer and the Nethe, which represent the easternmost tributaries united together in the Rupel, there is a whole range of rivieras which, converging together from every part of Belgium in a single point, 13 km. in S. of Antwerp, they unite in the lower Scheldt. All the tributaries then participate in the privilege of the Scheldt itself of being raised and enlivened by the sea flow, thus becoming maritime arteries at least for a few hours every day: on the Scheldt the flow is affected up to Ghent, 92 km. upstream of Antwerp, 172 km. from the sea mouth.
La Meuse (Bro. Meuse, flam. Maas), flowing in Belgium for only a fifth part of its course, here too has a slope like a plain river, although its path, far from unfolding in an open plain like that of the Scheldt, opens into a deep depression between high rock walls. The low slope has allowed the channeling of the river, thus making it well navigable by barges and steamers for the whole Belgian route; but the stretch that follows downstream in Dutch territory, since it is not settled, the value of the river in the channeled part is very limited. The regime suffers from abrupt and frequent irregularities, and especially dangerous are the sudden summer floods, when the Ardennes tributaries are swollen together with the main river, flowing with torrential waters on largely impermeable lands. The tributaries fed by the limestone of the Devonico and the Carbonico behave with regularity, among which the Lesse is particularly notable for its karst regime. It is the copious waters hidden in the bowels of these limestones that give the provident drinking sap to many cities of Brabant and Flanders. Major tributaries than the Lesse are the Sambre, originating from the French territory and confluent with the navigable course at Namur, and the Ourthe, although navigable, descending from the Ardennes and confluent at Liège, also with beds deeply depressed in the rocky assises of the plateau. The great straight furrow directed from O. to E., consisting of the single extension Sambre-Meuse, stands out as one of the master features of the Belgian country, very clearly engraved street and pulsating artery of industries.