I see triangles

To find fish on a rain­fed river, An­drew Ralph looks for shapes in the sur­face

Trout & Salmon (UK) - - CONTENTS -

A sim­ple way to read a river, sug­gested by An­drew Ralph

IT STARTED FOR ME A FEW YEARS ago when North Coun­try guide Stuart Min­nikin and I were fish­ing on Lan­cashire’s River Calder, near Burn­ley. We were chat­ting about tech­nique and landed on the sub­jects of rivercraft, wa­ter types within a pool, and fish lo­ca­tion. Stuart then men­tioned some­thing that has stuck with me ever since. He said: “It’s all about triangles.” What a rev­e­la­tion: Stuart’s triangles have helped me to read rivers and un­der­stand where trout lie and feed. Where are these triangles? You’ll find them in the fast-flow­ing parts of a rain­fed river, ar­eas of sig­nif­i­cant wa­ter vol­ume and ve­loc­ity, par­tic­u­larly at the pool head. Here the sur­face dis­tur­bance has a tri­an­gu­lar ap­pear­ance when viewed from the river­bank.

HOW A RAIN­FED RIVER FLOWS

There’s no need to un­der­stand the com­plex sci­ence of mov­ing wa­ter but I think all an­glers would ben­e­fit from some ba­sic knowl­edge. On rain­fed rivers, pools are, in the main, made of shal­low wa­ter fall­ing into a deep sec­tion and then lift­ing at the tail. This is re­peated over and over, cre­at­ing a dis­tinc­tive run-and-pool se­quence caused by wa­ter mov­ing at pace over rock and gravel. Wa­ter moves in lay­ers at dif­fer­ent speeds: it’s fastest at the sur­face, slow­est at the bot­tom. Wa­ter flow­ing down a river also has a fastest point, nor­mally in the cen­tre, but it can be to one side where bends, shal­lows, rocks or is­lands have an ef­fect. So we have a fastest point, a main chute of flow, which starts to slow as it nears both banks – hence a nat­u­ral tri­an­gle is formed. Fluid re­sis­tance is caused when wa­ter pass­ing at pace through, over or around rock and gravel meets the sur­face, per­haps at a vis­i­ble boul­der, the bank, an un­seen riverbed ob­struc­tion, or it could be a mar­ginal shal­low area. This con­tact causes fric­tion and slows the flow. The con­tin­ual flow and dis­place­ment of wa­ter is called tur­bu­lence by an­glers. An­other key point is that, the faster the flow, the greater the fric­tion and the more pro­nounced and vis­i­ble the tur­bu­lent area. It’s worth re­mem­ber­ing that the river is a liv­ing thing, al­ways chang­ing, and with only an ex­tra inch of wa­ter, a well-known pool can look com­pletely dif­fer­ent.

“We have a fastest point … which starts to slow as it nears both banks”

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