Aven de l'Hydre

The aven de l'Hydre opens in a level of Upper Jurassic limestone. The cleared entrance has a diameter of about fifty centimetres. It leads to an inclined bedding-plane crawl with an earthy floor, which indicates the dip of the limestone strata. a small chamber follows: in the middle, a first shaft opens, about 7 metres deep. At its base, the continuation is found between collapsed blocks and the wall; it leads to a second step, 5 metres this time. Then a short forced conduit opens onto the great 53-metre shaft, bell-shaped at the start, which then widens along a major N/S-trending fault. At its base, a 10-metre step gives access to the Grand Méandre (with a short upper level at the top of the R 10) following the North-South fault. The collapsed floor allows the descent of the second P 53; it is cut in its middle by an enormous block that forms a comfortable ledge, beware of rockfalls. From this ledge, a 27-metre descent reaches the bottom of the shaft at the -148.5m level. a pendulum on the right reaches the fossil network, a succession of P 10, P 12, P 27, still following meanders down to the -175m level where a constriction had stopped explorations. There are other conduits in this first part, notably a branch at the top of the P 53 leading to a series of parallel shafts (P 31, P 10, P 15, P 10), the salle de l'Onyx where a skylight returns to the top of the P 53, and the salle de la coulée: a section of upward gallery at the top of the great flowstone. The clearing of the constriction at -175m gave access to a series of new verticals: P11, P8, P12, P7, P12, P5, P7, and finally P40. At the bottom of the last shaft, a new constriction blocks progress, level reached -275m. At the top of the P 40 which leads to the former bottom of -275m, one enters a gently ascending meander. At the end, an easy 5 to 6 metre climb cuts across the arrival of a forced conduit that is followed downstream. At the base of the P 6, the conduit divides into two parts: the lower part is often partly obstructed by earthy deposits accumulated during the descent; prefer the forced conduit above, shaped like a 50 cm diameter tube, a little narrow on the way up, which allows this passage to be bypassed. The forced conduit then opens onto a major vertical fracture and a magnificent P 43 split in two; the shaft is very wide but the heavily decorated walls are fairly unstable on the last vertical (massive cauliflowers). One lands on a very spacious ledge before tackling the 25-metre shaft, just as beautiful. a squeeze in the formations gives access to a last 8m shaft. Just before the bottom of this shaft, a slight pendulum reaches a narrow forced conduit. a few more metres of climbing reveal a squeeze that allows a further descent of 5 to 6 metres; one then arrives at the lower part of this new network, at the -356m level. At this level, a narrow side conduit lets out a very violent draught, but a major dig is necessary to continue exploration.

In the gently ascending meander that starts from the top of the P 40, the walls are lined with magnificent cups; the place is very fragile and it is good to be as delicate as possible in order to preserve these places. The P 43 has heavily decorated walls, with massive cauliflowers.

Several steps are easy to downclimb, then a larger 6-metre step must be rigged; from that moment on the rope is never left. Then follows a P 5, then a P 6, a P 4 and a P 9, which must be rigged.

The exploration of the Réseau des Coupelles in the Aven de l'Hydre places it among the most important pits of the karsts of the Pyrénées-Orientales and the Aude.