The most unfortunate period for the river Mrežnica, ecologically speaking, is now behind us. Fifteen years ago there was a cellulose plant "Simo Dimić" operating in Plaški. Its waste was dumped in the river Dretulja. The abyss of Dretulja is tied beneath the service with the Mrežnica spring, and pollution was visible on the river Mrežnica. Those were huge "pillows" of yellow stinking foam which was formed mostly beneath the falls and in the calm parts of the river they looked like long white stains. During summer droughts and low water levels, it was forbidden to drink water from Mrežnica for the surrounding villages, and on several occasions even bathing wasn't recommended. Dead fish were often to be seen, and there was much less fish than today. Luckily the factory was shut down, but there are still tanks with dangerous chemicals in the factory, which could leak because of neglect, and pollute Dretulja and Mrežnica.

Construction of a dam on Zagorska Mrežnica, from where water is directed toward the hydro-electric plant "Gojak" on Dobra, took away 40% of Mrežnica's basin what disturbed the water regime of Mrežnica. Luckily average flow is still sufficient for the travertine dams, not to stay dry during low water levels, what would be devastating for the travertine dams. In this case Tounjčice is in a little worse position. In the summer, some parts of this river stay completely without water, so fish and crabs in the upper flow of the river, die.

The vicinity of the road Zagreb-Senj also has its negative effects, because of ecological incidents cause by overturning of tank trucks which transport fuel or dangerous chemicals. One such incident occurred in August 2001 by the bridge across Tounjčica in Tounj, when several hundred liters leaked into the river. In the area of shallow karst pollution also goes through the gaps in limestone rocks and with minimum filtration enter the water systems. Parallel with the road there is a railroad track Zagreb-Karlovac-Rijeka built in 1873.

Use of dynamite while poaching fish is one of the worst crimes man can do to the river and its ecosystem. Unfortunately Mrežnica isn't spared of this crime, especially during the war. Besides dynamite nets are regularly used, along with traps, so the fish are endangered even more.

In 1884 in Duga Resa, a textile factory was built, along with an hydro-electric power plant. The factory works today with half capacity, and pollution has diminished, but its still there. The factory drops chemicals for coloring into the river, so down the river we can see Mrežnica in various colors, red, blue, yellow…

In the Gornji Zvečaj area, on the bottom of the river there is the Adriatic Pipeline. Although the pipes and their connections are well welded and secured from the river current with trunks full of rocks, there is always the danger from unpredictable situations (cracks, tectonic movement).

In the area of rivers Mrežnica and Tounjčica there are two quarries. The quarry in Tounj is above the spring of Tounjčica where there is also an asphalt base. The quarry in Zvečaj is also in the vicinity of Mrežnica. Besides their distortion of the environment, vibrations caused by mining in quarries could disturb the sensitive static of travertine dams.

In the recent years one of old wounds of Mrežnica re-opened. It's the military installation "Eugen Kvaternik" on which there were common military maneuvers of American and Croatian armies held in years 2000 and 2001. It is questionable what kind of ammunition was used and maybe tested in these maneuvers, and non-official information testify about huge heaps of shells, deposited inside the installation site. The installation has no waste removal service, and it is buried in the surrounding pits. There was a lot of talk about jets which break the speed of sound and cause strong vibrations, which according to the words of experts, endanger static of travertine dams on Plitvice lakes.