SSRG International Journal of Civil Engineering Volume 10 Issue 1, 1-8, January 2023 ISSN: 2348-8352 / https://doi.org/10.14445/23488352/IJCE-V10I1P101 © 2023 Seventh Sense Research Group® This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Original Article Impact of Changes in Rainfall Patterns and Air Temperature on Water Balance in Danda Besar Swamp Irrigation Area Muhammad Chairi Munanjar 1 , Maya Amalia 2 1,2 Department of Civil Engineering, Faculty of Engineering, Lambung Mangkurat University, Indonesia Received: 12 November 2022 Revised: 19 December 2022 Accepted: 02 January 2023 Published: 14 January 2023 Abstract - Indonesia lies in a tropical climate area and depends on rainfall as the main source of irrigation. Changes in rainfall patterns and air temperature directly impact the water availability for irrigation purposes, including Danda Besar Swamp Irrigation Area (DIR). DIR Danda Besar is a tidal swamp irrigation field, but the tidal power cannot reach several areas, so it needs to use rainwater to supply water demand and becomes rainfed agriculture. The observation of changes in rainfall patterns and air temperature from 2001 to 2020 was conducted using daily TRMM (Tropical Rainfall Measurement Mission) data split into 2 observation periods: Period I from 2001 to 2010 and period II from 2011 to 2020. The data analysis process consists of validation and correction to the TRMM data before it is used for water balance analysis, calculation of effective rainfall for rice and evapotranspiration, and analysis of water availability and demand. From the comparison of water availability discharge between Period I (2001-2010) and Period II (2011-2020), the highest increase in mid-month water availability occured on December 1 and December 2, and the highest decrease in water availability occured on November 1 and November 2. The results of the water balance analysis are based on water demand according to the cropping scenario with two cropping scenarios. Water balance 1 has a deficit in water availability for Periods I and II; water balance 2 is recommended for cropping patterns due to climate change, so the water balance is calculated based on water availability for Period II. No water deficit in Water balance 2. Keywords - TRMM (Tropical Rainfall Measurement Mission), DIR Danda Besar, Water availability, Water demand, Cropping scenario. 1. Introduction Danda Besar Swamp Irrigation Area (DIR) locates at - 3.10799, 114.67021 coordinates. Based on Triadi B (2010) research, DIR Danda Besar is a tidal irrigation field with a hydrotopographic class of overflow types A, B and C. In 2021, the farmers stated that currently, tidal power could not reach the entire planting area, so it supplies the water demand with rainwater. DIR Danda Besar planting area and planting season, according to Agricultural Development Strategic Command Counselor (Kostratani) at BPP Rantau Badauh Petani in Danda Jaya Village, doing new planting in April to September with a planting area of 1460 hectares (Metro Kalimantan, 2020) and the area of DIR Danda Besar is 2200 ha. Several water resource development issues are unpredictable climate changes, such as floods, droughts, and storms (Hukom, Limantara, & Andawayanti, 2012). Rainfall and air temperature are variables that affect most to climate change the most. Rainfall will increase the water volume, which affects plant growth. Air temperature affects the process of photosynthesis, respiration, transpiration, pollination growth, fertilization and fruit falling. The influence is related to other factors such as humidity, water availability and type of plant (Hariadi, 2007). During the last 30 years, rainfall in DAS Ciliwung has fluctuactively increased, which resulted in water availability decreasing by 2 m 3 /sec (Ariyani, 2017). Changes in DAS Krueng Aceh since 2001 showed that climate change had decreased the mainstay discharge in April-December by 23,5% (Ferijal, Mustafril, & Jayanti, 2016). Rainfall pattern change in Way Mital irrigation area occurred in 2009 with an annual rainfall of 2315 mm, 4615 mm in 2001 and 3886 mm in 2008 (Hukom, Limantara, & Andawayanti, 2012). The purpose of this study is to analyze changes in rainfall patterns, including the decrease or increase in rainfall volume, shifts in wet, dry, and humid months and air temperature increase which directly impacts the water availability for irrigation in Barito Kuala, especially in DIR Danda Besar for the availability and demand of water for cropping patterns necessity. 2. Materials and Methods This study uses TRMM (Tropical Rainfall Measurement Mission) rainfall and climatological data from the NASA Prediction Of Worldwide Energy Resources (POWER) project by accessing the site https://power.larc.nasa.gov/data- access- viewer/ from 2001-2020. Observational rainfall data were obtained from Mandastana rain gauge data for 2008-