Introduction:
Water resources systems planning and design is an important subject in civil engineering that focuses on the management and utilization of water resources. To excel in this subject, it is essential to have access to reliable study materials and resources. Here are some suggestions for study materials that can help you in your preparation for this optional subject.

1. Textbooks:
Textbooks are an excellent source of in-depth knowledge and understanding of the subject. Some recommended textbooks for water resources systems planning and design include:
- "Water Resources Systems Planning and Management" by Daniel P. Loucks and Eelco van Beek.
- "Water Resources Engineering" by Larry W. Mays.
- "Water Resources Systems Analysis" by Mohan S. Wali.

2. Lecture Notes and Course Materials:
Lecture notes and course materials provided by your university or institute can be valuable resources for studying this subject. These materials are usually well-structured and cover all the important topics. They often include examples, case studies, and problem-solving exercises that can help you develop a deeper understanding of the subject.

3. Research Papers and Journals:
Research papers and journals are excellent resources for staying up-to-date with the latest developments and advancements in water resources systems planning and design. Reading research papers can also help you gain an in-depth understanding of specific topics and explore different perspectives.

4. Online Resources:
There are several online resources available that can supplement your learning. Some reliable websites include:
- EduRev: EduRev provides a wide range of study materials, notes, and practice questions for various subjects, including civil engineering. You can find comprehensive study materials specifically designed for water resources systems planning and design on their platform.
- National Institute of Hydrology (NIH): The NIH website offers a variety of publications, reports, and research papers related to water resources planning and management. These resources can help you gain insights into real-world applications of the subject.

5. Reference Books:
Reference books are useful for gaining additional knowledge and exploring different approaches and techniques. Some recommended reference books for water resources systems planning and design include:
- "Water Resources Systems Engineering: Planning, Analysis, and Management" by Larry W. Mays.
- "Handbook of Water Resource Systems: Planning and Management" by Slobodan P. Simonovic.

Conclusion:
To excel in the optional subject of water resources systems planning and design in civil engineering, it is important to have access to reliable study materials and resources. Textbooks, lecture notes, research papers, online resources, and reference books are all valuable sources of information that can help you develop a deep understanding of the subject. Utilize these resources effectively to enhance your knowledge and excel in your studies.