Gerhard became an independent environmental consultant in 1998, implementing a water biomonitoring programme for the larger companies in the forest industry. He has more than 23 years’ experience in the biomonitoring of aquatic systems, specializing in the monitoring of aquatic macro-invertebrates as indicators of ecosystem health. He also has experience in biotic indexes using fish, diatoms, dragon- and damselflies, riparian vegetation, and geomorphology, and knowledge in hydrology (flow) and water chemistry. He has implemented and applied biomonitoring work in streams and rivers in South Africa (Western Cape, Eastern Cape, KwaZulu-Natal, Mpumalanga, and Limpopo provinces), Swaziland, Mozambique, Zimbabwe, Malawi, DRC, Congo-Brazzaville, Angola and Uganda. Gerhard is also actively involved in assessing the distribution of Odonata (dragon- and damselflies), both adults and larvae, and contributes data to the National and African Odonata Database.