Will there be more mosquitoes because of the balancing lake?

No. Research shows that the balancing lake cause balancing lake additional mosquito nuisance.
The number of mosquitoes mainly depends on the weather. There are usually few mosquitoes in this area.

Is there a risk of livestock diseases such as bluetongue?

No. Bluetongue is spread by small insects (midges). These are mainly found in the vicinity of farms. Research shows that nature in De Onlanden plays almost no role in spreading this disease.