Waters, rocks and surface
In the middle of this area there is a low karstic plain 160 and 200m above sea level. Tectonic movement and limestone basis enables unique original of low karstic area, which is in some parts protected from formation of Karst with a thick layer of red clay. The plain stretches to hillside of the Gorjanci in the north and rises in less karstic and wooded Veliko Bukovje in the south east, which is almost 200m higher than the plain. The most important stone of Bela krajina are limestone and dolomites. Surface has a karstic looks because of cracked carbonate stone from the Jurassic period. The thickness of sediments in Kanižarica, which lies in the south of Črnomelj, is over 400m. Younger alluvions are only near the Kolpa and the Lahinja. On low karstic plain there are predominately slopes of under 6o  . Slopes between 6 and 20o  are found in higher areas. Here is also a big possibility of earthquakes.
Western outskirts of Bela krajina with Semič:

Almost the whole area of Bela krajina belongs to the river basin of the Kolpa. Because of its karstic surface river net is  thin and  most of the stream is under the surface. Waters which flow on the surface are springs and streams. The Kolpa gets water from the Lahinja and karstic springs. The Kolpa doesn't flow under the surface because it is strongly engraved in the limestone plateau. At first it flows from southwest to northeast. Near Croatian Ladoviæi it gets Dinarid direction, from Marindol to Metlika it flows towards north, and then towards east. Deep river-bed and small flood areas are characteristics of the Klopa . But when it  rains very heavily, the water starts to erupt from underground and floods cultivable areas. This only lasts some hours.
 The Kolpa walley between Bosljiva loka and Kuželj:

Middle year flow of the Kolpa near Metlika is 75m3 /s. Average month flow is the biggest in November and the smallest in August. In the most watery month there is on average three times more water than usually. The smallest flows of the Kolpa are usually in periods of long summer draught in the end of August, September or even in the beginning of October.The Lahinja biggest flows are in March and the lowest in July and August. First summer decrease of the Lahinja is very distinctive and is a consequence of hot and dry summer and hydrologic characteristics of low Bela krajina's Karst, which hardly keeps underground supplies of water. High summer temperatures of water are characteristics of Bela krajina rivers. Kolpa's temperature in summer rises even above 25o C.The Lahinja flows in very narrow river-bed, that is why it isn't as hot as the Kolpa.

Part of park "Lahinja" and Lower Bilpa:

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