chalk streams Flashcards
(34 cards)
what is a chalk stream?
habitat and ecology or perennial chalk stream headwaters and future challenges.
what gradient do chalk streams have and why?
low gradient, due to them forming from ocean beds, they’re very erodable.
what percentage of the annual discharge may derive from groundwaters?
90%
what is the temperature like in chalk streams?
relatively constant at around 11 degrees if a spring.
what is the hydrology and flow like in a chalk stream?
relatively persistent hydrology and flow with dampened discharge fluctuations.
what is the ratio between hydrology and flow?
3:1
why are floods rare in chalk streams?
due to the large storage capacity.
what is the substratum dominated by and why?
gravel, due to the geology, pebbles and gravel are sensitive to siltation, because of the low gradient and placid flow.
what temperature are chalk rivers?
around 5-17 degrees.
what are natural influences in chalk rivers?
feedback between organisms and the physical environment.
how does a protected area influence chalk streams?
the flow is altered due to organisms.
what are human influences on chalk streams?
structures such as mills, damns, ponds, drains, diches, and food defences.
what river and bank managements are put into place to protect chalk rivers?
weed cutting, bank protection, rehabilitation, bank poaching, runoff from agriculture, and water abstraction.
how does weed cutting protect the chalk rivers?
it makes it harder to fish due to the barrier and hydraulic resistance. if there is a lot of weeds, it will slow the water down and cause localised flooding.
why is bank protection important?
ensure they’re maintained, no eroding towards houses.
what is bank poaching?
when animals go into the water to drink or cool down and it causes the banks to erode away.
how many of England’s rivers are altered?
95% of all rivers in England are altered.
if we change one element of the chalk system, what effect does this have?
bottom-up- limited top. top-down- influences the whole structure. food webs and trophic interactions may get altered.
a question to think about: is there a predominance of generalist or specialist feeders?
?
a question: can we diagnose the causes of past changes and can we predict the impact of contemporary change?
?
a question: can we use science to underpin decisions for the future?
?
what will happen if a tree was put above the river?
there will be fewer algae, therefore this will affect the primary consumers.
which level will be completely affected if algae decrease?
the primary consumers, but only if that is their main food source or only food source.
how do you know if a chalk stream is meeting expectations?
if you know what to expect to do with eh conditions and the number of species.
