The Semarang City Government prohibits groundwater/deep wells in hotel and apartment buildings because the use of groundwater or deep wells in locations that have experienced subsidence will further aggravate the subsidence. The method used in this research is to purposively select hotel and apartment buildings in Semarang that have received an assessment by the Semarang City Building Expert Team and have received a certificate of serviceability. Furthermore, compare the map of land subsidence in some areas of the city of Semarang with the natural water sources used by the hotel and apartment buildings. The research results showed that from 10 hotel and apartment buildings, there were 7 that used deep wells in zone level II, namely subsidence between 2.1 to 4 cm/year. Meanwhile, 3 other hotel and apartment buildings use water from the Municipal Drinking Water Company of Semarang. The existence of hotel and apartment buildings that use groundwater/deep wells in zone level II will increase and trigger the more significant subsidence in the area, thereby increasing the level of subsidence to level III.

Water use during peak hours and daily maximum are two interrelated terms in water usage patterns. Fluctuations in water use can be determined by planning standards, namely, estimates of peak hour and daily factors, so as to optimize air production and improve services. This study aims to calculate the maximum peak hour and daily factors. This research was carried out in the Special Region of Yogyakarta with a sampling technique carried out using a stratified proportional random sampling as many as 200 respondents. The results showed that the use of water at peak hours was 266.73 liters / day, which was in the morning between 06.00 and 08.00 am, while the maximum daily use of water is 774.09 litres/day which is on Sunday. The peak hour factor in the Special Region of Yogyakarta is 1.30 and the maximum daily factor is 1.26, when compared to the standard established by the Directorate General of Human Settlements, Ministry of Public Works, the peak hour factor is 1.5 while the daily maximum is 1.1. This means that the peak hour and maximum daily factors cannot be generalized in the Special Region of Yogyakarta.

River basin management can increase biodiversity conservation, land productivity, ecosystem restoration, rehabilitation, and land reclamation. River basin management cannot be handled by one institution alone but requires cooperation and coordination with various parties. Community involvement in river basin management has a strategic role and is carried out based on the principle of sustainability that combines a balance between productivity and conservation to achieve river basin management goals. Community participation has the power to make decisions autonomously in order to be able to solve the needs and interests of life and improve the standard of living by utilizing the resources that must be owned. In addition, it is also necessary to harmonize structural relationships between institutions in government both at the center and at the local level so that internal factors can be controlled, and programs and activities do not overlap in the management of natural resources and air. One of the impacts of climate change is the occurrence of river basin damage. Upstream river basins as buffer areas, water catchments, and sources of water filters will be damaged. Sensitive people will be more vulnerable, while people who can adapt will survive.

The Babon River in East Semarang has been polluted by heavy metals sourced from industrial waste. So that water pollution at the Babon River estuary does not spread, it is necessary to carry out water treatment. This research uses a glass aquarium reactor and utilizes yellow velvetleaf (limmoncharis Flava) and water spinach (Ipomoea aquatic fork) plants as a medium to reduce the concentration of copper ions (Cu2+) by using variations in detention time. The results and analysis showed that yellow velvetleaf and water spinach could reduce the concentration of copper ions (Cu2+) in estuary surface water within 1 hour, 2 hours, 3 hours, and 5 hours. After going through several stages of a simple drinking water pre-treatment process, the results showed that yellow velvetleaf plants could reduce the concentration of copper ions (Cu2+) in Babon river water samples, from an initial concentration of 0.055 mg/L to 0.020 mg/L, with the highest efficiency percentage reduction up to 61.5%. As for water spinach, the concentration of copper ions that can be reduced only reaches the lowest level of 0.047 mg/L, with the highest percentage reduction efficiency of only 9.6% after the same pre-treatment process.